LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 


Class 


STANDARD   SPECIFICATIONS    FOR    STRUCTURAL 
'STEEL— TIMBER— CONCRETE    AND   REIN- 
FORCED CONCRETE 


Published    by  the 

McGraw-Hill    Book.  Company 

Yorlc 


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STANDARD  SPECIFICATIONS 


FOR 


STRUCTURAL  STEEL-TIMBER-CONCRETE 
AND   REINFORCED   CONCRETE 


BY 

JOHN  C.  OSTRUP,  C.E. 

CONSULTING    ENGINEER 

Professor  of  Structural  Engineering,  Stevens  Institute  of  Technology;  Member  American 

Society  of  Civil  Engineers;    Member  Institution  of  Civil  Engineers; 

Member  American  Society  Promotion  Engineering  Education; 

Member  American  Society  Advancement  of  Science, 

etc.,  etc. 


OF    THE 

UNIVERSITY 

OF 


McGRAW-HILL    BOOK    COMPANY 

239   WEST   39TH   STREET,   NEW   YORK 
6  BOUVERIE  STREET,  LONDON,  E.G. 
1910 


CONTENTS 


PART  PAGE 

I.  STEEL  FRAMEWORK  OF  BUILDINGS 1 

II.  HIGHWAY  BRIDGES 13 

III.  RAILROAD  BRIDGES 26 

IV.  PLATE  GIRDERS 37 

V.  MATERIALS  AND  WORKMANSHIP 43 

VI.  INSPECTION,  PAINTING  AND  ERECTION :  54 

VII.  STRUCTURAL  TIMBER 58 

VIII.  CEMENT 65 

IX.  PORTLAND-CEMENT  CONCRETE 70 

X.  REINFORCED  CONCRETE 75 

vii 


Of   THE 

UNIVERSIT 

^LlFQKj 


STANDARD     SPECIFICATIONS     FOR    STRUC- 
TURAL STEEI^-TIMBER-CONCRETE  AND 
REINFORCED   CONCRETE 


PART  1 

STEEL   FRAMEWORK   OF   BUILDINGS 

DEAD,  Sxow,  AND  WIND  LOADS 

1.  The  Dead  Load  upon    any  part  of  a  structure  shall  con- 
sist  of  the  calculated  weight  of  the  materials  and  fixtures  carried 
permanently  by  such  part. 

2.  The    actual    weight    of   the   different    materials   shall    be 
computed    as   accurately  as   possible    and,  if   necessary,  a  trial 
design  shall  be  made  to  ascertain  the  weight  of  any  portion  in 
doubt. 

3.  Roof  Covering.     The  weight  of  roof  covering  will  average, 
for  each  square  foot  of  superficial  roof  area,  as  follows: 

Corrugated  steel 2-3  Ibs. 

Shingles 4-6  " 

Roofing  tiles 6-8  " 

Slate  (i  to  J"  thick) 6-8  " 

Gravel  and  composition 8-10  " 

Terra-cotta,  2"  thick  (flat  arch) 10-15  " 

Concrete,  per  inch  thickness  (flat  arch). .  10-12  " 

Plank  sheathing,  per  inch  thickness 3-4  " 


2  STANDARD  SPECIFICATIONS 

4.  Purlins.     The    weight    of   purlins   will    average,    for   each 
square  foot  of  superficial  roof  area,  as  follows: 

Steel  purlins  ..........................   2-3     Ibs. 

Wooden  purlins  ......................     3-5      " 

5.  Roof  Trusses.     The  weight  of  ordinary  steel  roof  trusses, 
having  a  pitch  of  £  to  J,  will  average,  for  each  square  foot  of 
horizontal  area,  as  follows: 


w=i6o(L+10)' 


or  for  the  total  weight  of  one  truss, 


where  W  =  total  weight  of  truss  in  Ibs. 

c=  weight  in  Ibs.  per  sq.ft.  on  horizontal  area  carried  by 
truss. 

d=  distance  in  feet  between  trusses,  provided  that  d^  — 

5 

(Par.  23). 
L  =span  in  feet  of  truss. 

6.  Snow  Load.     In  latitudes  between  40°  and  50°  the  snow 
load  shall  be  taken  per  horizontal  square  foot  of  roof  area  «as 
follows  : 

Pitch  from  flat  to  £  inclusive  ..........  25  Ibs. 

"      over  J-  to  J  "       ..........  20     " 

"    i  to  i  "       ..........  15     " 

"    i  to  i  "       ..........  10     " 

"     i  and  more  ..........       0     " 

In  other  latitudes  these  snow  loads  should  be  modified  according 
to  local  conditions. 

7.  Wind    Pressure.     The    wind    pressure    shall    be    taken    as 
30    Ibs.  per    sq.ft.,  upon    the  entire  exposed    area  of    the    steel 
framework,  or  upon  the  vertical  projection  of  sides  and  ends  of 
roof  and   building,  and  as  acting  horizontally  in  any  direction. 


STEEL  FRAMEWORK  OF  BUILDINGS  3 

8.  Minimum  Roof  Load.      The  minimum  roof  load,  which 
will  include  the  dead,  snow,  and  wind  loads,  shall  be  taken  as 
follows : 

On  roof   covering   and   purlins,   40  Ibs.   per   sq.ft. 

of  superficial  area. 
On  roof  trusses,  40  Ibs.  per  sq.ft.  of  horizontal  area. 

LIVE  LOADS 

9.  Live  Loads  on  Floors. 

(a)  The  live  loads  on  floors  shall  be  considered  as  being  uni- 
form over  their  entire  area  and  shall  be  taken,  as  a  minimum, 
per  square  foot  as  follows : 

Dwellings,  apartment  houses,  hotels, 

hospitals 50  Ibs.  and  up 

Office  buildings 60 

Schools,  theaters,  churches 75 

Ordinary  stores,  public  buildings .  .  .    100 
Warehouses,  factories,  armories 200         " 

When  designing  flooring,  joists,  girders,  etc.,  the  probability  of 
concentrated  loads,  such  as  pianos,  safes,  machinery,  wagons, 
etc.,  must  be  considered  and  provided  for. 

(6)  The  above  live  loads,  except  in  warehouses  and  other 
buildings  exposed  to  simultaneous  loading  on  all  floors,  may 
be  reduced  for  columns  as  follows: 

Columns  supporting  roof  and  top  floor,  no  reduction. 

11  next  ten  floors,  a  cumulative  reduction 
of  5  per  cent  for  each  succeeding 
floor. 

"  "          remaining    floors,    a    total    reduction 

of   50   per   cent. 

10.  Crane  Loads.     The  actual  weight  of  the  crane,  its  dimen- 
sions and  its  lifting  capacity  shall  be  used  if  obtainable,  other- 
wise the  following  data  for  Typical  Electrical  Traveling  Cranes* 
shall  be  used: 

*  Mr.  C.  C.  Schneider  in  Trans.  Am.  Soc.  C.  E.,  Vol.  54. 


STANDARD  SPECIFICATIONS 


Weight  of  Rail 

-IT'l                1 

Maximum 

"\Vl   m~>1 

per  Yard  for 

Capacity. 

Span. 

\\  heel 
Base. 

\\  neel 
Load  in 
Pounds. 

s. 

V. 

Plate 
Girders. 

Beams. 

Ft.  In. 

Inches. 

Feet. 

Pounds. 

Pounds. 

5  Tons 

f  40 
I  60 

8  6 
9  0 

12,000 
13,000 

10 
10 

7 

7 

40 
40 

40 
40 

10     " 

J40 

9  0 

19,000 

10 

7 

45 

40 

.L  \J 

160 

9  6 

21,000 

10 

7 

45 

40 

15     " 

/  40 

9  6 

26,000 

10 

7 

50 

50 

I  60 

10  0 

29,000 

10 

7 

50 

50 

[40 

10  0 

33,000 

12 

8 

55 

50 

20 

160 

10  6 

36,000 

12 

8 

55 

50 

25     " 

(40 

10  0 

40,000 

12 

8 

60 

50 

160 

10  6 

44,000 

12 

8 

60 

50 

30     " 

[40 

10  6 

48,000 

12 

8 

70 

60 

\60 

11  0 

52,000 

12 

8 

70 

60 

40     " 

(40 

11  0 

64,000 

14 

9 

80 

60 

\60 

12  0 

70,000 

14 

9 

80 

60 

50     " 

/40 

11  0 

72,000 

14 

9 

100 

60 

160 

12  0 

80,000 

14 

9 

100 

60 

where  s  =  Side  clearance  from  center  of  rail. 
v  =  Vertical  clearance  from  top  of  rail. 

(a)  A  wheel-load  shall  be  assumed  as  distributed  in  the  top 
flange,  over  a  distance  equal  to  depth  of  girder,  with 
a  maximum  of  30  inches. 

(6)   In  addition  to  the  vertical  load,  the  top  flanges  of  the 
girder  shall  withstand  a  lateral  loading  of  two-tenths 
(i¥)    of    the    lifting     capacity    of    the     crane,    equally 
divided  between  the  four  wheels  of  the  crane. 
ii.  Impact  Loads.     For  beams,  girders,  and  columns  carry- 
ing traveling  cranes  an  allowance  of  25  per  cent  of  the  computed 
moments  and  shears  due  to  same  shall  be  added  to  compensate 
for  the  effects  of  impact  and  vibration. 


UXIT  STRESSES:  STEELWORK 

12.  In  designing  the  component  parts  of  any  building  the 
maximum  stresses  due  to  the  combined  effects  of  axial  stresses 
and  bending  stresses  from  dead,  snow,  wind  and  live  loads,  includ- 
ing impact,  if  any,  shall  not  exceed,  for  structural  steel  and  rivet 
steel,  the  following  values  in  /6s.  per  square  inch,  except  as  modi- 
fied in  Pars.  14-16. 


STEEL  FRAMEWORK  OF  BUILDINGS  5 

(a)  Axial  tension  in  main  members,  net  section     16,000  Ibs. 

in  wind  bracing,  "  20,000    k" 

(b)  Betiding,  net  section,  on  extreme  fibers  of: 

Rolled  shapes,  built  sections  and 

plate  girders 16,000  Ibs. 

Pins 20,000     " 

(c)  Axial  compression  in  main  members,  gross  section, 

5  =  16,000-70^-, 

where  «S=  allowable  unit  stress. 

/=  unsupported  length  of  member  in  inches. 

r  =  least  radius  of  gyration  of  member  in  inches.    (Per.  39.) 

(d)  Shear  on:  Turned  bolts,  and  field  rivets 

when  hand  driven.  . . .'..- 7,500  Ibs. 

Field  rivets  when  power  driven.  9,000     " 

Shop  rivets  and  pins 10,000     " 

Plate  girder  webs,  gross  section.  10,000     " 

(e)  Bearing  on:  Turned  bolts  and  field  rivets 

when  hand  driven 15,000  " 

Field  rivets  when  power  driven.  18,000  " 

Shop  rivets  and  pins 20,000  " 

13.  Expansion  Rollers. 

Allowable  pressure  per  lin.  in 600d 

where  d=  diameter  of  roller  in  inches. 

14.  Combined  Stresses.     When  the  effect  of  bending  stresses 
due  to  wind  loading   is  considered  and  added  to  the  axial  and 
bending  stresses,  due  to  other  causes,  the  above  unit  stresses 
(Par.  12)  may  be  increased  25  per  cent. 

15.  Eccentric  Stresses.     Provision  must  be  made  for  eccen- 
tric loading  on  columns  and  other  members.     Whenever   angles 
used  as  wreb  members  or    bracing  are  connected  up  by  one  leg 
only,  the  above  unit  stresses  (Par.  12)  shall  be  decreased  25  per 
cent. 

1 6.  Reversal    of    Stresses.     Members    and    connections    sub- 
ject to  reversal  of  stresses  shall  be  proportioned  for  an  equivalent 
stress  equal  to  that  stress  which,  when  added  to  50  per  cent  of 
the  other,  will  give  the  greater  section. 


6  STANDARD  SPECIFICATIONS 

17.  Cast    Iron.     The    maximum    stresses    shall    not    exceed , 
in  pounds  per  square  inch,  for 

Tension 2,500  Ibs. 

Compression  (on  blocks) 12,000     " 

Shear 1,500     " 

UNIT  STRESSES:  MASONRY,  FOUNDATIONS 

1 8.  Pressure   on   Walls.     The   pressure   on   walls   caused   by 
beams,  girders,  wall  plates,  etc.,  shall  not  exceed  the  following 
values  in  pounds  per  square  inch. 

On  brickwork,  laid  in  lime  mortar.  ...  150  Ibs. 

cement  mortar.  200  " 

On  terra-cotta,  hollow 75  " 

solid 150  " 

On  cinder  concrete  1:2:6 125  " 

On  Portland  cement  concrete  1:2^:5.  275  " 

1:2   :4.  350  " 
On  ordinary  rubble  masonry,  cement 

mortar 150  " 

On  first-class   stone  masonry,  cement 

mortar 400-600  " 

19.  Pressure    on    Foundations.     The    pressure    on    masonry 
or  foundations  caused  by  column  bases,  etc.,  shall  not  exceed 
the  following  values  in  pounds  per  square  inch: 

Dimension  stones 125  Ibs. 

Portland  cement  concrete  1:2^:5 300     " 

1:2   -A 400     " 

1:2:0    (grani- 
toid) . .   600     " 
Other  values  as  given  above  (Pars.  17,  18). 

20.  Pressure    on    Soils.     The    pressure    on    soils    caused    by 
foundations,  walls,  etc.,  shall  not  exceed  the  following  values  in 
tons  per  square  foot: 


STEEL  FRAMEWORK  OF  BUILDINGS  7 

Earth,  ordinary H  tons 

"      tamped  or  naturally  solid 3  " 

Clay,  soft 1  " 

"      dry  or  mixed  with  dry  sand 2  " 

"      hard  pan 3  " 

"      hard  and  mixed  with  coarse  sand.  .  .  4  " 

Sand    and   gravel  mixed,   when   dry  and 

coarse 6  " 

Rock,  broken  or  partly  disintegrated 5-25  " 

Rock,  solid  bed 200  " 

21.  Bearing  Power  of  Piles.  Wooden  piles  shall  be  spaced 
not  less  than  30  in.  c.  to  c. 

When  the  piles  are  driven  through  wet  and  loose  soil  to  a 
good  bearing  the  pressure  shall  not  exceed  300  Ibs.  per  sq.  in. 
of  their  average  cross-section.  When  driven  through  a  firm  soil 
this  pressure  may  be  increased  to  600  Ibs.  (Pars.  270,  277.) 


DESIGN  OF  FRAMING 

22.  Roof  Trusses.     Roof  trusses  shall  preferably  be  of  such 
type  as  wrill  allow  the  purlins  to  be  placed  only  at  the  panel 
points.     Wherever  this   is    neither  practicable  nor   economical, 
the  top  chord  shall  be  designed  for  both  bending  and  direct 
stresses. 

Roof  trusses  shall  be  riveted  throughout,  except  in  special 
cases  for  long  spans  where  the  field  splices  and  main  joints  may 
be  pin-connected. 

23.  Spacing  of  Roof  Trusses.     The  spacing  of  roof  trusses 
shall  preferably  be  such  as  to  allow  only  the  use  of  single  rolled 
shapes  as  purlins  (Par.  26).     Whenever  this  limit  be  exceeded 
intermediate  jack-rafters  may  be  used.     For  ordinary  roofs  the 
most  economical  spacing  of  trusses  will  generally  be  as  follows: 


For  spans  up  to        40  ft.  16'  0"  c.  to  c. 

"    from  40-55    "  17'  0" 

"  55-70    "  18'  0" 

"  70-85    "  19'  0" 

"        "        "  85-100"  20'  0"         " 


8  STANDARD  SPECIFICATIONS 

24.  Pitch  of  Roofs.     The  pitch  must  vary  according  to  cir- 
cumstances, but  shall  preferably  be  made  as  follows: 

For  tar  and  gravel  roofs  .........  from  ^  to  -^ 

"      tile,    corrugated    steel    and 

shingled  roofs  ..........      "     i  to  J 

slate  roofs  .................      "     ^  and  up 


" 


25.  Bracing.     Roof  trusses  shall  be  braced  in  pairs;  in  the 
plane  of  the  top  chord  the  bracing   may  be  made  adjustable, 
whereas  in  the  plane  of  the  bottom  chord  the  bracing  must  be 
rigid. 

Bracing  in  planes  of  the  sides  and  ends  of  buildings  may  also 
be  made  adjustable. 

Knee-braces  must  be  provided  wherever  practicable,  for 
instance,  between  trusses  and  columns  and  between  crane 
girders  and  columns. 

26.  Purlins.     Both  steel  and  timber  purlins  shall  be  attached 
to  the  roof  trusses  by  means  of  lug  angles.     Steel  purlins  shall 
be  composed  of  single-rolled  shapes  (Z-bars,  Us,  I-beams  and  Ls) 
whenever  possible,  and  be  of   a   depth  5;  than   one-thirtieth    (^) 
of  the   span.     Otherwise  plate   girder   or  lattice   girder  purlins 
shall  be  used,  and  no  trussed  purlins  will  be  permitted. 

Purlins  shall  generally  be  spaced  from  4  ft.  to  5  ft.  apart  for 
all  forms  of  roof  covering  except  reinforced  concrete,  where  the 
spacing  may  be  increased  to  12  ft. 

27.  Girts.     Girts  shall  be  attached  to  columns  by  means  of  lug 
angles  and  shall  be  composed  of  single  rolled  shapes.     They  shall 
generally  not  be  spaced  more  than  4  ft.  apart. 

28.  Beam  Girders.     Beams  composed  of  single  rolled  shapes 
(I-beams   and    Us)    shall   be  proportioned   by  their    moment   of 
inertia. 

No  beam  shall  be  used  whose  flange  width  is  less  than  one- 
twentieth  (-2J0)  of  the  span  length,  unless  its  compression  flange 
is  properly  supported  sidewise  against  buckling.  When  more 
than  one  beam  is  used  to  form  a  girder,  they  shall  be  connected 
by  bolts  and  separators,  so  as  to  bring  the  unsupported  flange 
width  within  the  above  ratio,  spaced  with  a  maximum  limit  of 
5  ft.  Beams  used  in  floors  shall  have  a  depth  of  not  less  than 
one-twentieth  (^0)  of  the  span  length;  they  shall  be  riveted 


STEEL  FRAMEWORK  OF  BUILDINGS  9 

to  the  columns,  whenever  such  occur,  by  means  of  connection 
angles  which  must  carry  the  entire  load.  Shelf  angles  may  be 
provided  for  convenience  during  the  erection.  The  free  end 
of  such  floor  beams  must  be  securely  anchored  to  the  walls. 

29.  Plate  Girders  (see  Part  IV). 

DETAILS  OF  DESIGN 

30.  Minimum  Size  of  Material.     Xo   rolled   shape   or  metal 
of  less  thickness  than  J  in.  shall  be  used  except  for  fillers.     No 
angles  shall  be  less  than  2£"X2"Xi"  and  no  rivets,  except  in 
beam  connections  and  lacing  bars,  shall  be  less  than  }  in.  in 
diam.     (Pars.  33,  38,  45,  46.) 

31.  Details  of  Joints.     Main  members  of  trusses  shall  be  so 
arranged   around  the  joints  that  their  neutral  axes  will  meet 
in  a  common  point. 

All  joints  in  riveted  work,  whether  in  tension  or  in  compres- 
sion, shall  be  fully  spliced. 

32.  Details  of  Connections.    The  strength  of  connections  shall 
be  such  as  to  cause  the  main  member  to  fail  should  the  combina- 
tion be  tested  to  destruction.     Xo  connection,  except  for  lattice 
bars,  shall  have  less  than  two  rivets. 

33.  Rivets.     In  main  members  composed  of  angles  the  maxi- 
mum diameter  of  rivet  used  shall  not  exceed  one-quarter   (^) 
the  width  of  leg  through  which  it  passes.     Three-quarter   (J) 
in.  rivets  shall  not  be  countersunk  in  plates  less  than  f  in.  in 
thickness  and   f-in.  rivets  shall  not    be  countersunk    in  plates 
less  than  ^  in.  in  thickness. 

Except  in  bed  plates,  no  rivet  shall  be  of  less  diameter  than 
the  thickness  of  the  thickest  plate  through  which  it  passes. 

34.  Rivet   Spacing.     The  minimum  pitch  shall  never  be  less 
than  three  diameters  of  the  rivet  and,  if  possible,  not  less  than 
3"  for  I"  rivets,  2£"  for  J"  rivets,  2J"  for  f"  rivets,  and  1 1"  for 
i"  rivets. 

The  maximum  pitch  of  rivets,  in  the  direction  of  the  stress, 
shall  not  exceed  6  in.,  or  16  times  the  thinnest  outside  plate  con- 
nected, and  not  more  than  40  times  that  thickness  at  right  angles 
to  the  stress,  except  when  two  or  more  plates  in  contact  are  to 
be  held  together,  where  the  pitch  may  be  12  in.  in  any  direction. 

The  maximum  pitch  at  ends  of  built  up  compression  mem- 


10  STANDARD  SPECIFICATIONS 

bers  shall  not  exceed  four  diameters  of  the  rivet  for  a  length 
equal  to  two  times  the  width  of  the  member. 

35.  Edge  Distance  of  Rivets.     The  minimum  distance  from 
the  center  of  any  rivet  hole  to  a  sheared  edge  shall  be  1%"  for 
J"  rivets,  1J"  for  J"  rivets,  H"  for  f "  rivets,  and  I"  for  £"  rivets, 
and  to  a  rolled  edge,  except  in  flanges  of  I-beams  and  channels, 
1J",  1J",  1"  and  -J"  respectively.     The  maximum  distance  from 
any  edge  shall  be  eight   (S)   times  the  thickness  of  the  outside 
plate,  but  shall  not  exceed  5  in. 

36.  Tension  Members.     In  calculating  the  net  area  of  tension 
members  the   area  of  rivet   holes  must  be  deducted,   assuming 
the  diameter   of  the  hole  J  in.   larger  than   the  nominal   size  of 
the   rivet. 

Main  tension  members  shall  be  composed  of  sections  placed 
symmetrically  about  the  central  plane  through  the  truss.  Second- 
ary tension  members  may  be  made  of  a  single  shape.  (Par.  15.) 

Pin-connected  riveted  tension  members  shall  have  a  net 
section  through  the  pin  hole  25  per  cent  in  excess  of  that  through 
the  body  of  the  main  member.  The  minimum  net  section  back 
of  the  pin  hole,  parallel  to  the  axis  of  the  member,  shall  not  be 
less  than  that  through  the  body  of  the  main  member. 

37.  Eye-bars.     Heads    of   eye-bars    shall    be    forged   and    so 
proportioned  as  to  develop  the  full  strength  of  the  bar.     (Par. 
43.) 

The  eye-bars  shall  be  placed  in  the  truss  so  as  to  be,  as  nearly 
as  possible,  parallel  to  its  central  plane,  the  maximum  incli- 
nation being  limited  to  1  in.  in  16  ft. 

38.  Rods.     The  minimum  size  of  bracing  rods,   or  laterals, 
shall  be  f  in.  in  diameter  and  they  shall  be  upset  at  the  screw  ends. 
The  minimum  size  of  sag  rods  shall  be  f  in.  in  diameter,  but  these 
need  not  be  upset. 

39.  Compression  Members.     Main  compression  members  shall 
be  composed  of  sections  placed  symmetrically  about  the  central 
plane  through  the  truss.     Sub-struts  may  be  made  of  a  single 
shape.     (Par.  15.) 

Xo  compression  member  shall  have  a  length  exceeding  120 
times  its  least  radius  of  gyration,  except  those  used  for  wind  and 
lateral  bracing,  which  may  have  a  maximum  length  of  140  times 
their  least  radius  of  gyration. 

40.  Tie-Plates.     The    open    sides    of    compression    members 


STEEL  FRAMEWORK  OF  BUILDINGS  11 

shall  be  stayed  by  diagonal  lattice  having  tie-plates  as  near  each 
end  as  practicable  and  at  intermediate  points  where  the  lattice 
is  interrupted.  In  the  main  members  the  tie-plates  shall  have 
a  length  of  not  less  than  the  width  of  the  main  member  on  the 
connected  side,  provided  that  no  tie-plate  be  less  than  10  in.  long 
near  the  ends  of  such  members. 

Their  minimum  thickness  shall  be  one-forty-eighth  (^F)  of  the 
distance  between  center  lines  of  the  connecting  rivets. 

41.  Columns.     In  proportioning    the    area    of    columns    the 
effect  of  bending  stresses  due  to  wind  or  eccentric  loading  shall 
be  included. 

Columns  shall  have  as  few  splices  as  practicable  and,  where 
spliced,  the  splices  shall  be  strong  enough  to  resist  the  direct 
as  well  as  the  bending  stresses. 

42.  Lattice  Bars.     Single  lattice  bars  shall  have  an  inclination 
of  approximately  60°  with  the  axis  of  the  main  member  and  shall 
have  a  minimum  thickness  of   one-fortieth  (T^)  of  the  distance 
between  the  rivets  connecting  them  to  the  member. 

Single  lattice  bars  may  be  connected  with  one  rivet,  except 
in  flanges  more  than  5  in.  wide,  where  two  rivets  shall  be 
used.  Lattice  angles  shall  be  connected  by  at  least  two  rivets. 

Double  lattice  bars  shall  be  used  where  the  distance  between 
rivet  lines  in  the  flanges  exceeds  15  in.  They  shall  have  a  mini- 
mum thickness  of  one-sixtieth  (-fa)  of  the  distance  between  the 
rivets  connecting  them  to  the  member,  shall  have  an  inclination 
of  approximately  45°,  and  shall  be  riveted  at  their  intersection. 

The  minimum  width  of  lattice  bars  shall  be: 


For  lo-m.  channels,  or  built  sections  with]  ot  .      /7  . 

,              „  .  f  2^  in.  (J-in.  rivets) 

angles  over  3  in j 

For  12-,  10-,  and  9-in.  channels,  or  built  sec-  ]  01  .       _  . 

.  ,   0  .  \  21  in.  (f-in.  rivets) 

tions  with  3-m.  angles I 

For  8-  and  7-in.  channels,  or  built  sections  ]  _ 

.  ,   01  .  \  2  -in.  (f-in.  rivets) 

with  2^-in.  angles j 

For  6-in.  channels  or  less 1}  in.  (Vin.  rivets) 

43.  Pins.  The  minimum  diameter  of  pins  shall  be  eight- 
tenths  (T%-)  of  the  width  of  the  widest  eye-bar  attached  to  it. 

Members  shall  be  packed  on  pins,  using  filling  rings  where 
necessary,  in  a  manner  that  will  prevent  any  lateral  movement. 


12  STANDARD  SPECIFICATIONS 

44.  Pin  Holes.     Pin  holes  shall  be  reinforced  by  plates  where 
necessary.     The   plates   shall   be   of   such   size   as  to   distribute 
properly,  through  sufficient  rivets;  the  pin  pressure  to  the  webs 
and  their  flanges  in  each  segment  of  the  main  member. 

45.  Wall  Plates  and   Column  Bases.     The  minimum  thick- 
ness shall  be  J  in.  for  wall  plates  and  J  in.  for  base  plates.     The 
wall  plates  and  column  bases  shall  be  detailed  and  placed  in  such 
a  manner  that  the  load  will  be  evenly  distributed,  using  cement 
mortar  or  grout  for  filling  if  necessary. 

They  shall  be  of  sufficient  size  and  thickness  so  as  not  to 
exceed  the  allowable  unit  stresses.     (Pars.  12,  14,  17,  18  and' 19.) 

46.  Anchor  Bolts.     Columns   shall   be  anchored   to  the  foun- 
dations, by  means  of  anchor  bolts,  when  stressed  in  tension  at 
their  base.     The   minimum   diameter   of   anchor  bolts   shall   be 
|  in.  upset;  they  shall  be  of  sufficient  length  to  engage  a  mass 
of  masonry,  the  weight  of  which  shall  be  1J  times  the  tension. 

The  anchor  bolts  shall  in  all  cases  be  of  sufficient  size  to 
resist  in  shear  any  horizontal  force  acting  thereon. 

47.  Temperature.     Where  necessary  provision  shall  be  made 
for  expansion  and  contraction  covering  a  range  of  150°  F 

48.  Expansion  Rollers.     The   minimum   diameter  of  expan- 
sion rollers  shall  be  4  in. 


PART  II 

HIGHWAY   BRIDGES 
GENERAL  REQUIREMENTS 

49.  Classification.     Highway  bridges  may,  based  upon  traffic 
conditions,  be  divided  into  three  classes,  viz.: 

Class  A — City  bridges,  subject  to  heavy  traffic. 

Class  B — City,    Interurban    or   Country   bridges,  subject 

to  medium  traffic,  and 
Class  C — Country  bridges,  subject  to  light  traffic. 

50.  Type    of   Bridge.     The  following  types  of  bridges  shall 
preferably  be  used: 

For  spans  up  to    20  f t . ,  wooden  beams  or  rolled  beams. 

"       "    from    20  to    40  ft.,  rolled  beams  or  pi  ate  girders. 
"      40  to    70  ft.,  plate  girders. 
"       80  to  100  ft.,  plate  girders  or  riveted  trusses. 
"     100  to  160  ft.,  riveted  trusses. 
"  long  spans,  160ft.  and  over,  pin-connected  trusses. 

Pony  trusses  shall  be  avoided  wherever  possible,  but  may 
be  used  for  spans  from  40  to  90  ft.     (Par.  80.) 

51.  Materials.     All  parts  of  the  superstructure,  except  the 
flooring  and  paving,  shall  be  of  structural  steel,  or  rivet  steel. 

Cast  iron  may  be  used  for  minor  parts  and  for  ornamental 
purposes;  all  other  castings  shall  be  of  steel. 

52.  Clearances.     All  through  bridges   carrying   electric    cars 
shall  have  a  clear  head-room,  above  the  top  of  the  rail,  of  at 
least  15  ft.,  for  a  width  of  6  ft.  over  the  center  of  the  track. 
Where  the  track  is  straight  there  shall  be   clear  width  of  at  least 
7  ft.  on  each  side  of  the  center  of  the  track  at  a  height  of  12  in. 
above  the  top  of  rails.     Where  the  tracks  are  curved,  the  addi- 

13 


14  STANDARD  SPECIFICATIONS  • 

tional  clearance  shall  be  computed  by  assuming  the  extreme 
length  of  car  as  45  ft.,  width  8  ft.,  and  distance  between  centers 
of  trucks  20  ft. 

Through  bridges,  not  carrying  electric  cars,  shall  have  a 
minimum  head-room  of  14  ft.  above  roadway,  for  classes  A  and 
B,  and  of  12  ft.  6  in.  for  class  (7,  unless  otherwise  required  by 
local  ordinances. 

53.  Paved  Floors.     Pavements    consisting    of    stone   blocks, 
paving  bricks,  asphalt,  etc.,  resting  upon  a  bed  of  concrete,  not 
reinforced,  shall  be  supported  upon  buckled  or  corrugated  plates. 
The  minimum  thickness  of  this  concrete  bed  shall  be  3  in.  for 
the  roadway  and  2  in.  for  the  sidewalks.     Such  floors  shall  be 
pitched  transversely  and  proper  provisions  for  their  thorough 
drainage  shall  be  made. 

Pavements  consisting  of  wooden  blocks  may  rest  on  a  timber 
floor,  consisting  of  planks  laid  transversely  and  at  least  4  in. 
thick. 

54.  Wooden  Floors.     (See  Pars.  271,  279  to  281.) 

55.  Cross-Ties.     (See  Par.  283.) 

56.  Guard-Rails.     (See  Par.  284.) 

57.  Handrailing.     A   handrailing   3   ft.    6   in.   high   shall   be 
placed  on  each  side  of  the  bridge,  except  where  plate  girders 
serve   the   same   purpose.     Where   the   handrailing   is   of   rolled 
steel  or  cast  iron  it  shall  be  of  pleasing  design  and  shall  be  rigidly 
attached   to   the    superstructure.     For   wooden   handrailing   see 
Par.  282. 

58.  Approaches.     All  floor-timbers,  rails,   guards  and  hand- 
railings  shall  extend  over  all  piers  and  abutments  and  shall  make 
suitable  connection  with  the  embankments  at  either  end  of  the 
structure. 

LOADS 

59.  Dead  Load.     The  dead  load  consists  of: 

(a)  The  weight  of  the  steelwork; 

(b)  The  weight   of  the  paving,  if  any; 

(c)  The  weight  of  the  wooden  flooring,  if  any,  and 
((I)  The  weight  of  the  electric  railway  tracks,  if  any, 

The  approximate  weight  of  the  steelwork  shall  be  obtained 
either  by  trial  design  or  otherwise. 

The  weight  of  the  paving  shall  be  taken  at  160  Ibs.  per  cu. 


HIGHWAY  BRIDGES  15 

ft.  for  stone  blocks,  at  150  Ibs.  per  cu.  ft.  for  paving  bricks,  and 
at  130  Ibs.  per  cu.  ft.  for  concrete  and  asphalt. 

The  weight  of  the  wooden  flooring  shall  be  taken  at  4^  Ibs. 
per  foot-board  measure  for  oak,  yellow  pine  and  other  hard 
woods,  at  3£  Ibs.  per  foot-board  measure  for  white  pine  and 
other  soft  woods. 

The  minimum  .weight  of  cross-ties  and  guard  rails  shall  be 
taken  at  200  Ibs.  per  lin.ft.  of  each  track,  and  the  weight  of  rails, 
fastenings  and  splices  at  100  Ibs.  per  lin.ft.  of  each  track. 

60.  Live  Loads.  All  bridges  shall  be  designed  to  carry  cer- 
tain concentrated  and  certain  uniformly  distributed  loads,  as- 
specified  below,  placed  so  as  to  give  the  greatest  stress  in  each 
part  of  the  structure. 

(a)  Class  A.  For  the  floor  system  and  local  truss  mem- 
bers a  concentrated  load  of  40,000  Ibs.,  distributed  on  two 
axles  8  ft.  centers  and  5  ft.  gauge  (occupying  a  length 
of  20  ft.  and  a  width  of  10  ft.),  and  upon  the  remaining 
area  of  the  floor,  including  sidewalks,  a  load  of  100 
Ibs.  per  sq.ft. 

For  the  trusses  or  girders,  100  Ibs.  per  sq.ft.  of  entire 
roadway  and  sidewalks  for  spans  of  100  ft.  or  less,  80 
Ibs.  for  spans  of  200  ft.  or  over,  and  proportionally  for 
intermediate  spans. 

(6)  Class  B.  For  the  floor  system  and  local  truss  members 
a  concentrated  load  of  30,000  Ibs.,  distributed  on  two 
axles  8  ft.  centers  and  5  ft.  gauge  (occupying  a  length 
of  20  ft.  and  a  width  of  10  ft.),  and  upon  the  remaining 
area  of  the  floor,  including  sidewalks,  a  load  of  90 
Ibs.  per  sq.ft. 

For  the  trusses* or  girders,  90  Ibs.  per  sq.ft.  of  entire 
roadway  and  sidewalks  for  spans  of  100  ft.  or  less,  70 
Ibs.  for  spans  of  200  ft.  or  over  and  proportionally  for 
intermediate  spans. 

(c)  Class  C.  For  the  floor  system  and  local  truss  members 
a  concentrated  load  of  20,000  Ibs.,  distributed  on  two 
axles  8  ft.  centers  and  5  ft.  gauge  (occupying  a  length 
of  20  ft.  and  a  width  of  10  ft.),  and  upon  the  remaining 
area  of  the  floor,  including  sidewalks,  a  load  of  80  Ibs. 
per  sq.ft. 

For  the  trusses  or  girders,  80  Ibs  per  sq.ft.  of  entire 


16  STANDARD  SPECIFICATIONS 

roadway  and  sidewalks  for  spans  of  100  ft.  or  less,  60 
ibs.  for  spans  of  200  ft.  or  over,  and  proportionally 
for  intermediate  spans. 

(d)  Electric  Railways.  Any  bridge  carrying  electric  railway 
tracks  (excepting  those  for  exclusive  railroad  use)  shall 
in  addition  to  one  of  the  above  loadings  be  designed  to 
carry  on  each  track  a  series  of  cars,  each  weighing 
100,000  Ibs.,  unless  otherwise  specified.  This  load  to  be 
distributed  equally  on  two  trucks  20  ft.  centers,  each 
having  two  axles  5  ft.  centers  and  5  ft.  gauge  (occupy- 
ing a  length  of  40  ft.  and  a  width  of  10  ft.  ) 

61.  Impact.     An   impact   allowance   shall    be   added   to   the 
computed  maximum  live  load  stresses,  as  follows: 

Tor  bridges  of  all  classes  carrying  highway  ]  T  0/    100 

traffic  onl    ............    .....    .... 


For  bridges,  or  part  of  bridges,  carrying!  _  „/    200    \ 

electric  railway  traffic  ..............  J       pa  \/^f300/; 

where  8=  computed  maximum  live  load  stress,  moment  or  shear; 
L  =  loaded  length  of  span  in  feet. 

No  impact  allowance  shall  be  added  to  stresses  produced  by 
wind,  centrifugal  or  traction  forces. 

62.  Wind  Pressure.  The  wind  bracing  shall  be  designed  to 
resist  one  of  the  following  lateral  loadings,  whichever  produces 
the  greater  stress: 

(a)  Structure  unloaded.  50  Ibs.  per  sq.ft.  on  the  exposed 
surface  of  all  trusses  and  the  floor  as  seen  in  eleva- 
tion, or 

(6)  Structure  loaded.  (Bridges  of  all  classes  carrying  highway 
traffic  only),  30  Ibs.  per  sq.ft.  on  the  exposed  surface 
of  all  trusses  and  the  floor  as  seen  in  elevation  in  addi- 
tion to  a  uniform  load  of  150  Ibs.  per  lin.ft.  of  structure 
applied  on  the  "  loaded  "  chord,  or 

(c)  Structure  loaded.  (Bridges  of  all  classes  carrying  electric 
railway  traffic)  the  same  loading  as  under  (6),  except 
that  the  additional  uniform  lead  is  300  Ibs.  per  lin.ft. 
of  structure  and  is  applied  7  ft.  above  the  base  of  rail. 


HIGHWAY  BRIDGES  17 

The  minimum  value  of  the  above  pressures  shall  be  250  Ibs. 
per  lin.ft.  for  the  " loaded"  and  150  Ibs.  for  the  "unloaded" 
chord  of  the  structure. 

Trestles  shall  in  addition  to  one  of  the  above  wind  loadings 
be  designed  to  resist  a  pressure  of  200  Ibs.  for  each  vertical  foot 
of  bent  in  height. 

The  above  wind  pressure  shall  in  all  cases  be  treated  as 
moving  loads.  (Par.  61.) 

63.  Centrifugal  Force.     Any  structure  on  a  curve  carrying 
an  electric  railway  shall  be  designed  to  resist  a  lateral  force  of 
10  per  cent  of  the  equivalent  live  load  per  lin.ft.,  applied  5  ft. 
above  the  top  of  rail.     (Par.  61). 

64.  Traction    Force.     Any    structure    carrying    an    electric 
railway  shall  be  designed  to  resist  a  longitudinal  force   of  20 
per  cent  of  the  greatest  live  load  placed  upon  the  same. 


UNIT  STRESSES 

65.  Structural  Steel.  In  designing  the  component  parts  of 
any  highway  structure  the  maximum  stresses  due  to  the  com- 
bined effects  from  dead  and  live  loads,  including  impact,  or  due 
to  wind  pressure,  centrifugal  and  traction  forces,  shall  not  exceed 
for  structural  steel  and  rivet  steel,  the  following  values  in  Ibs. 
per  square  inch,  except  as  modified  in  Pars.  71  to  74. 

(a)  Axial  tension,  net  section 16,000  Ibs. 

(6)  Bending,  net  section,  on  extreme  fibers  of  rolled 

shapes  (Par.  77),  built  sections  and  plate  girders  16,000  " 
Joists,  under  concentrated  loads,  when  flooring 

is  non-continuous  (Par.  77) 20,000  " 

Pins,  on  extreme  fibers ..,,." 24,000  ' ' 

(c)  Axial  compression,  gross  section, 


S  =16,000  -70- 


where  S  =  allowable  unit  stress, 

/  =  unsupported  length  of  member  in  inches, 

r  =  least  radius  of  gyration  of  member  in  inches  (Par.  96). 


18  STANDARD  SPECIFICATIONS 

(d)  Shear  on:    turned    bolts    and   field    rivets,   when 

hand  driven 9,000  Ibs. 

Field  rivets,  when  power  driven.  . 1  1,000  ' ' 

Shop  driven  rivets  and  pins 12,000   " 

Plate  girder  webs,  gross  section 10,000  ' ' 

(e)  Bearing  on:  turned  bolts    and  field   rivets,  when 

hand  driven 18,000  ' ' 

Field  rivets,  when  power  driven 22,000  " 

Shop-driven  rivets  and  pins 24,000  ' ' 

66.  Pressure    on     Foundations.     The   pressure    on   masonry 
foundations  shall  not  exceed  the  following  values   in  pounds  per 
square  inch : 

Portland  cement  concrete  1:2:4  and  first-class  sandstone 

or  limestone  masonry,  including  impact 400  Ibs. 

Portland  cement  concrete  1:2:0  (granitoid)  and  first-class 

granite  masonry,  including  impact 600  ' ' 

67.  Pressure  on  Soils.     For  allowable  pressures  see  Par.  20. 

68.  Timber.     For  allowable  stresses  see  Part  VII. 

69.  Expansion  Rollers. 

Allowable  pressure  per  lin.in GOOc/ 

where  d  =  diameter  of  roller  in  inches. 

70.  Cast  Steel.     The  maximum  stresses  shall  not  exceed,  in 
Ibs.  per  square  inch,  for, 

Tension 16,000  Ibs. 

Compression  (on  blocks) 16,000  ' ' 

Shear 10,000  ' ' 

71.  Combined  Stresses.     All  members  in  a  structure  exposed 
to  bending  stresses  from  a  transverse  loading,  due  either  to  the 
weight  of  the  member  itself,  or  to  the  weight  of  the  floor  system 
when  it  rests  directly  on  one  of  the  chords,  shall  be  designed  for 
the  maximum  combination  of  such  stresses  with  the  axial  stresses, 
including  impact  for  each   kind   of  loading,   using  an  extreme 
fiber  stress  of  16,000  Ibs.  per  sq.in. 

Where  the  bending  stresses  are  due  only  to  the  weight  of  the 


HIGHWAY  BRIDGES  19 

member  itself  and  do  not  exceed  1600  Ibs.  per  sq.in.,  the  effect 
may  be  neglected,  otherwise  the  maximum  unit  stresses  (Pars. 
65  and  73)  may  be  increased  10  per  cent. 

The  bending  moment  in  chord  segments  of  riveted  structures, 
or  in  pin-connected  members  when  continuous  over  joints,  shall 
be  computed  from  the  compromise  formula, 

A/ =±1.2  ivL2, 

where  M  =  positive  moment   at   center  or  negative  moment   at 

the  joint, 

u'  =  total  transverse  load  in  Ibs.  per.lin.  ft., 
7,  =  length  of  member  in  feet. 

72.  Eccentric     Stresses.      Whenever    angles,    used    as    web 
members  or  bracing,  are  connected  up  by  one  leg  only  the  above 
unit  stresses  (Par.  65)  shall  be  decreased  25  per  cent. 

73.  Maximum    Stresses.     When  combining  the  stresses  due 
to  vertical  forces  with  those  due  to  lateral  forces,  including  the 
direct  and  indirect  wind   stresses,   centrifugal  forces,  and  bend- 
ing stresses  in  the  end  posts  due  to  wind,  the  specified  unit  stresses 
(Pars.  65  and  71)  may  be  increased  25  per  cent,  provided  that 
this  combination  gives  a  greater  sectional  area. 

74.  Reversal  of  Stresses.     Where  the  stresses  due  to  wind 
and  centrifugal  forces  reverse  the  stresses  in  a  member  due  to 
vertical  forces  proper  provisions  must  be  made  for  the  piece  to 
resist  compression. 

Members  and  connections  subject  to  reversal  of  stresses 
shall  be  proportioned  for  an  equivalent  stress  equal  to  that  stress 
which,  when  added  to  50  per  cent  of  the  other,  will  give  the 
greater  section,  both  impacts  included. 

DESIGN  OF  STRUCTURE 

75.  General    Dimensions.     The    following    dimensions    shall 
first  be  calculated  or  assumed : 

Span  of  girders,  center  to  center  of  bearings. 
Span  of  trusses,  center  to  center  of  pedestals  or  end  pins. 
Span  of  floor-beams,  center  to  center  of  girders  or  trusses. 
Span  of  joists  or  stringers,  center  to  center  of  floor-beams 
or  one  panel  length. 


20  STANDARD  SPECIFICATIONS 

Depth  of  girders,  center  to  center  of  gravity  of  chords. 
Depth  of  trusses,  center  to  center  of  gravity,  or  center  to 
center  of  pins,  of  chords. 

76.  General    Proportions.      The    width    between    centers    of 
trusses   carrying   a   single   straight   electric   railway   track   shall 
not  be  less  than  15  ft.,  or  for  any  bridge  less  than  one-twentieth 
(-Jy)  of  the  span. 

The  depth  of  plate-girder  spans  shall  preferably  not  be  less 
than  one-twelfth  (-^)  of  the  span,  the  depth  of  lattice  girders 
and  pony  trusses  shall  not  be  less  than  one-tenth  (^)  of  the  span, 
and  the  depth  of  riveted  and  pin  connected  through  trusses  shall 
preferably  not  be  less  than  one-eighth  (-J-)  of  the  span,  or  less  than 
the  panel  length. 

77.  Floor   Framing.      Steel   joists   and   stringers   shall   pref- 
erably be  riveted  to  the  web  of  the  floor  beams.     Rolled  beams 
used  as  joists  shall  be  spaced  not  to  exceed  3  ft.  center  to  center 
and  shall  not  have  a  depth  of  less  than  one-twentieth  (-^-0-)   of 
the  span. 

If  the  floor  plank  be  continuous  each  joist  may  be  assumed 
to  carry  only  two-thirds  (J)  of  the  concentrated  load.  The 
top  flanges  of  stringers  must  be  provided  with  securely  bolted 
wooden  shims  for  the  purpose  of  spiking  the  planking  thereto. 

When  end  floor  beams  are  not  used  over  the  masonry  the 
joists  shall  have  their  ends  rigidly  connected  by  means  of  struts 
and  the  stringers  by  means  of  cross  frames. 

Floor  beams  shall  preferably  be  arranged  so  as  to  be  per- 
pendicular to  the  girder  or  truss  at  the  panel  points;  they  may 
rest  upon  the  top  chord  in  deck  bridges,  but  in  through  bridges 
they  shall  be  riveted  to  the  verticals. 

Rolled  beams  used  as  joints,  stringers,  or  floor  beams  shall  be 
proportioned  by  their  moment  of  inertia. 

78.  Plate    Girders.     For  plate  girders  used  as  stringers,  floor 
beams,  and  main  girders,  see  Part  IV. 

79.  Beam    Bridges.      When    bridges    carrying    electric    rail- 
ways are  built  of  rolled  beams  they  shall  be  braced  as  follows: 
With  a  single  beam  under  each   rail  and  for  spans  under    20  ft. 
the  bracing  shall  consist  of  cross  channels  framed  at  each  end  at 
intervals  not  exceeding  5  ft.,  for  spans  over  20  ft.  a  cross  channel 
framed  at  each  end  with  an  intermediate  diagonal  bracing.     When 
two  or  more  beams  are  placed  under  each  rail  the  beams  shall 


HIGHWAY  BRIDGES  21 

be   provided    with   riveted   or   cast-iron   separators   spaced   not 
over  5  ft. 

80.  Pony    Bridges.     The  top  chord  of  pony  trusses  shall  be 
securely  stayed  at  each  panel  point  by  means  of  gusset  plates, 
knee  braces,  or  wide  web  members  of  angles  with  lattice  or  web 
plate  when  efficiently  connected  to  the  floor  beams. 

81.  Deck  Bridges.     Trusses  in  deck  bridges  shall    be    pro- 
vided at  each  panel  point  in  the  bottom  chord  with  vertical 
sway  bracing  sufficiently  strong  to  carry  the  lateral  forces  to 
which  they  are  subjected. 

82.  Through    Bridges.     All  trusses  shall  be  so  designed  that 
the  stresses  may  be  determined  with  reasonable  accuracy;   they 
shall  have  stiff  hip  verticals,  and  in  the  bottom  chord  the  two 
end  segments  shall  also  be  made  rigid  whenever  the  stresses 
reverse  or  are  near  that  point. 

All  web  members,  including  counters,  except  for  long  spans 
(Pars.  50,  94,  95),  shall  be  made  rigid. 

83.  Bracing.     Ends  of  all  through  spans  shall  be  provided 
with  portals  of  rigid  design,  which  shall  be  as  deep  as  the  required 
clearance  (Par.  52)  will  allowr,  and  in  the  end  posts  proper  pro- 
vision shall  be  made  for  the  bending  stresses  produced  by  such 
portals. 

All  the  intermediate  panel  points  in  the  top  chord  of  through 
spans  shall  be  provided  with  transverse  struts  with  knee  braces 
or  with  vertical  sway  bracing.  The  struts  shall  be  made  of 
four  angles  laced  and  shall  have  the  same  depth  as  the  chord, 
to  the  upper  and  lower  face  of  which  they  shall  be  riveted  by 
means  of  connection  plates. 

In  the  plane  of  the  "  loaded  "  chord  ends  of  all  bridges  shall 
be  provided  with  lateral  struts  where  no  end  floor  beams  are  used. 

Lateral,  longitudinal  and  transverse  bracing  in  all  structures 
shall  be  composed  of  rigid  members. 

84.  Steel  Trestles.     Each  trestle  bent  shall  be  composed  of 
two   columns  braced  together  and,   when  battered,  the  batter 
shall  generally  not  be  less  than  1  horizontal  to  8  vertical  or  more 
than  1  horizontal  to  4  vertical. 

The  majority  of  the  bents  shall  be  united  in  pairs,  forming 
a  tower,  which  shall  be  rigidly  braced  on  all  four  sides  and  shall 
have  four  horizontal  struts  at  its  base. 

The  column  feet  shall  be  secured  to  the  foundations  bv  means 


22  STANDARD  SPECIFICATIONS 

of  details  and  anchor-bolts  capable  of  resisting  one  and  one- 
half  (H)  times  the  specified  lateral  (Pars.  62,  63)  and  longitu- 
dinal forces.  (Pars.  64,  104.) 

85.  Wooden  Trestles.     (See  Pars.  285,  286,  287.) 

86.  All  Structures.     Structures  shall  be  so  designed  that  all 
parts  will  be  accessible  for  inspection,  cleaning,  and  painting. 

Pockets  or  depressions  which  would  hold  water  shall  have 
drain  holes,  or  be  filled  with  waterproof  material. 

DETAILS  OF  DESIGN 

87.  Minimum    Size    of    Material.     No    rolled    shape,   except 
channels,  or  metal  of  less  thickness  than  ^  in.,  shall  be  used 
except  for  fillers.     The  webs  of  channels  shall  not  be  less  than 
|  in.     Xo  angles  shall  be  less  than  2^//X2^-//X^//7  and  no  rivets, 
except  in  beam  connections,  lattice   and   railings,   shall  be  less 
than  f  in.  in  diam.     (Pars.  95,  101.) 

88.  Details  of  Joints.     Main  members  of  trusses  shall  be  so 
arranged   around  the  joints  that  their  neutral  axes  will  meet 
in  a  common  point. 

The  sections  of  top  chords  and  inclined  end  posts  generally 
consist  of  two  rolled  or  built-up  channels  and  a  cover  plate;  such 
unsymmetrical  sections  must  be  so  proportioned  as  to  bring  the 
neutral  axis  near  the  center  of  the  webs.  (Par.  90.) 

Abutting  joints  in  compression  members  when  faced  .for 
bearing  shall  be  spliced  on  four  sides  sufficiently  to  hold  the  con- 
necting members  accurately  in  place. 

All  other  joints  in  riveted  work,  whether  in  tension  or  in 
compression,  shall  be  fully  spliced. 

89.  Details    of    Connections.     The    strength   of    connections 
shall  be  such  as  to  cause  the  main  member  to  fail  should  the 
combination  be  tested  to  destruction.     (Par.   90.) 

Xo  connection  except  for  lattice  bars  or  lattice  angles  shall 
have  less  than  three  rivets. 

All  joists  and  stringers  shall  preferably  be  attached  to  the 
floor  beams  by  means  of  connecting  angles  and  shall,  wherever 
possible,  rest  upon  shelf  angles  stiffened  by  vertical  angles  if 
necessary.  The  rivets,  however,  in  such  shelves  shall  not  be 
assumed  to  carry  any  part  of  the  shear. 

The    calculated   number   of   rivets    connecting   the    stringers 


HIGHWAY  BRIDGES  23 

to  the  floor  beams  and  the  floor  beams  to  the  trusses  shall  be 
increased  by  25  per  cent. 

Where  sidewalks  are  placed  outside  the  trusses,  and  supported 
on  brackets,  the  connection  shall  preferably  be  made  by  means 
of  a  fully  riveted  tension  plate,  as  no  tension  on  rivet  heads  will 
be  allowed. 

90.  Riveted  Work.     In  riveted  work  the  main  members  shall 
be  arranged,  wherever  practicable,  so  that  the  effective  sectional 
area  is  placed   symmetrically  about  the  two  principal  neutral 
axes.     (Par.  88.) 

Where  two  connected  members  have  their  centers  of  gravity 
in  a  continuous  line  the  rivets  in  the  splice  plates  must  be  arranged 
symmetrically  about  these,  using  the  minimum  pitch  (Par.  34), 
and,  by  staggering  or  otherwise,  have  as  few  rivets  as  possible 
in  planes  parallel  and  perpendicular  to  the  axis  of  the  member. 

Where  two  members  are  connected  by  means  of  gusset  plates 
the  rivets  must  be  arranged  symetrically  about  both  inter- 
secting center  lines  of  gravity. 

The  secondary  stresses  due  to  non-compliance  with  these  rules 
must  be  provided  for  in  the  joint  by  increasing  the  area  of  splice 
or  gusset  plates  and  the  number  of  rivets,  or  both. 

91.  Rivet  Spacing.     (See  Par.  34.) 

92.  Edge  Distance  of  Rivets.     (See  Par.  35.)    ' 

93.  Tension  Members.     In  calculating  the  net  area  of  tension 
members  the  area  of  rivet  holes  must  be  deducted,  assuming 
the  diameter  of  the  hole  |-  in.  larger  than  the  nominal  size  of  the 
rivet. 

Main  tension  members  shall  be  composed  of  sections  placed 
symmetrically  about  the  central  plane  through  the  truss.  Sec- 
ondary tension  members  mav  be  made  of  a  single  shape.  (Par. 
72.) 

Pin-connected  riveted  tension  members  shall  have  a  net 
section  through  the  pin  hole  25  per  cent  in  excess  of  that  through 
the  body  of  the  main  member.  The  minimum  net  section  back 
of  the  pin  hole,  parallel  to  the  axis  of  the  member,  shall  not  be 
less  than  that  through  the  body  of  the  main  member. 

94.  Eye-bars.     Heads  of  eye-bars  shall  be  forged  and  so  pro- 
portioned as   to    develop   the    full  strength  of   the  bar.     (Par. 
43.) 

The  eye-bars  shall  be  placed  in  the  truss  so  as  to  be,  as  nearly 


24  STANDARD  SPECIFICATIONS 

as  possible,  parallel  to  its  central  plane,  the  maximum  inclina- 
tion of  any  bar  being  limited  to  1  in.  in  16  ft. 

Adjustable  eye-bars,  when  used  as  counters,  shall  have  the 
screw  ends  upset  and  shall  be  provided  with  turnbuckles,  or  with 
sleeve  nuts  provided  with  holes  drilled  through  two  opposite  faces. 

95.  Rods.     All   rods   shall  have   the  loop   ends  forged   and, 
when  used  as  counters,  shall  have  the  screw  ends  upset  and  shall 
be  provided  with  turnbuckles  or  special  sleeve  nuts.     (Par.  94.) 
The  minimum  size  of  all  rods  shall  be  one  (1)  sq.in. 

96.  Compression  Members.      In  compression  members  form- 
ing chord  segments  as  much  as  possible  of  the  metal  shall  be 
concentrated  in  the  webs  and  flanges  and  the  neutral  axis  shall 
be  as  near  as  possible  to  the  center  of  the  web. 

In  all  compression  members  the  minimum  thickness  of  each 
single  web  plate  shall  be  one-fortieth  (-£$)  of  the  distance 
between  the  inner  lines  of  rivets  connecting  it  to  the  flanges,  and 
when  two  or  more  plates  form  a  compound  web,  the  minimum 
thickness  of  each  plate  shall  be  ^  in.  (Par.  34.) 

The  minimum  thickness  of  cover  plates  shall  be  one-forty- 
eighth  (Jg-)  of  the  distance  between  rivet  lines. 

The  minimum  thickness  of  flange  angles,  unsupported  by 
cover  plates,  shall  be  one-sixteenth  (^)  of  the  width  of  the  un- 
supported leg. 

No  compression  member  shall  have  a  length  exceeding  120 
times  its  least  radius  of  gyration,  except  those  used  for  wind 
and  lateral  bracing,  which  may  have  a  maximum  length  of  140 
times  their  least  radius  of  gyration. 

97.  Tie-Plates.     (See  Par.  40.) 

98.  Lattice  Bars.     (See  Par.  42.) 

99.  Pins.     (See  Par.  43.) 

100.  Pin  Holes.     (See   Par.   44.) 

101.  Column    Bases    in    Trestles.     Column    bases    shall    be 
made  of  plates  and  shapes  riveted  together,  and  no  cast  bases  or 
pedestals  will  be  allowed,  except  when  permitted  by  the  engineer. 
(Par.  84.) 

Xo  metal  in  the  bases  shall  be  less  than  one-half  (^)  in.  in 
thickness  and  the  base  plates  shall  not  be  less  than  three-quarter 
(I)  in. 

The  bases  shall  be  placed  on  all  bearing  surfaces  and  so 
anchored  as  to  allow  for  expansion. 


HIGHWAY  BRIDGES  25 

102.  Anchor  Bolts.     (See  Par.  46.) 

103.  Camber.     All    through    truss    bridges    shall   be    given 
a  camber  by  making  the  panel  length  of  the  top  chords,  or  their 
horizontal   projections,   longer   than   the    corresponding   panels 
of  the  bottom  chord  in  the  proportion  of  J  in.  in  10  ft. 

104.  Temperature.     Provision  shall  be  made  for  a  free  expan- 
sion and  contraction  of  all  parts,  corresponding  to  a  variation 
of  150°  F.  in  temperature. 

For  bridges  less  than  80  ft.  in  length  one  end  shall  be  free 
to  move  upon  smooth  surfaces. 

Bridges  of  80  ft.  and  over,  resting  on  masonry,  shall  have 
hinged  bolsters  or  shoes  at  both  ends,  and  at  one  end  the  shoes 
shall  rest  upon  a  nest  of  turned  expansion  rollers,  of  not  less  than 
4  in.  in  diameter  (Par.  69),  moving  between  planed  surfaces. 
(Par.  86.) 

In  very  high  trestle  towers  one  foot  shall  be  fixed,  two  feet 
shall  be  fixed  in  one  direction  only,  and  the  fourth  shall  be  free 
to  move  in  both  directions. 


PART  III 

RAILROAD   BRIDGES* 
GENERAL  REQUIREMENTS 

105.  Material.     The  material   in  the  superstructure   shall  be 
structural  steel,  except  rivets,  and  as  may  be  otherwise  specified. 

1 06.  Clearances.     On    a    straight    line    the    clear  height    of 
through  bridges  shall  not  be  less  than  21  ft.  above   the  top    of 
rails  for  a  width  of  6  ft.  over  a  single  track,  and  the  clear  width 
shall  not  be  less  than  7  ft.  from  the  center  line  of  the  track  between 
the  heights  of  4  and  17  ft.  above  the  rails. 

The  width  shall  be  increased  to  provide  the  same  minimum 
clearance  on  curves,  for  a  car  80  ft.  long,  14  ft.  high,  and  60  ft. 
center  to  center  of  trucks,  allowance  being  made  both  for  curva- 
ture and  superelevation  of  rail. 

107.  Cross  Ties.     (See  Par.  283.) 

108.  Guard  Rails.     (See   Par.    284.) 

LOADS 

109.  Dead  Load.     The  dead  load  shall  consist  of  the  estimated 
weight  of  the  entire  suspended  structure. 

The  approximate  weight  of  the  steelwork  shall  be  obtained 
either  by  trial  design  or  otherwise. 

The  weight  of  the  ballast  shall  be  taken  at  100  Ibs.  per  cu.ft. ; 
the  weight  of  the  timber  shall  be  taken  at  4J  Ibs.  per  foot-board 
measure,  with  a  minimum  of  250  Ibs.  per  lin.ft.  of  track,  and  of 
rails,  fastenings,  and  splices  at  150  Ibs.  per  lin.ft.  of  track. 

no.  Live  Loads.  The  live  loads,  for  each  track,  shall  consist 
of  two  typical  engines  followed  by  a  uniform  load,  according 

*  Adapted  from  General  Specifications  for  Steel  Railroad  Bridges,  1906, 
American  Railway  Engineering  and  Maintenance  of  Way  Association. 
L,  26 


RAILROAD  BRIDGES  27 

to  Cooper's  series,  or  a  system  of  loading  giving  practically 
equivalent  stresses.  The  minimum  loading  shall  be  Cooper's 
E.40,  as  shown  in  the  following  diagrams: 


im  »  »  »  •   &  AAAA   s  s  s  s  4'°°oib8- ^ un-ft- 

QQQQ     n  o  n  o  ^n    QOQO o  o   o  o 


FIG.  1. 


(F\  (T^     4)00° lb-'  P61" lln- ft- 
or         


FIG.  2. 


The  diagram  that  gives  the  larger  stresses  shall  be  used. 

in.  Heavier  Loading.  Heavier  loadings  shall  be  propor- 
tional to  the  above  diagrams  on  the  same  spacing. 

112.  Impact.  An  impact  allowance  shall  be  added  to  the  com- 
puted maximum  live  load  stresses,  as  follows: 


«/    300    \ 
Impact  =  S I      ,  30Q  ) , 


where  S=  Computed  max.  live-load  stress,  moment  or  shear. 

L=  Loaded  length  of  track  in  feet  producing  the  maximum 
stress  in  the  member.  For  bridges  carrying  more 
than  one  track  the  aggregate  length  of  all  tracks 
producing  the  stress  shall  be  used. 

No  impact  allowance  shall  be  added  to  stresses  produced  by 
traction,  centrifugal  and  lateral  or  wind  forces. 

113.  Lateral  Force.     All  spans  shall  be  designed  for  a  lateral 
force  on  the  "  loaded  "  chord  of   200  Ibs.  per  lin. ft.  plus  10  per 
cent  of  the  specified  train  load  on  one  track,  and  200  Ibs.  per 
lin. ft.  on  the  "unloaded"  chord;  these  forces  being  considered 
as  moving. 

114.  Wind  Pressure.     Viaduct  towers  shall  be  designed  for 
a  force  of  50  Ibs.  per  sq.ft.  on  one  and  one-half  (1£)  times  the 
vertical   projection   of   the   structure   unloaded;  or   30   Ibs.    per 
sq.ft.  on  the  same  surface  plus  400  Ibs.  per  lin.ft.  of  structure 
applied  7  ft.  above  the  rail  for  assumed  wind  load  on  train  when 


28  STANDARD  SPECIFICATIONS 

the  structure  is  either  fully  loaded  or  loaded  on  either  track  with 
empty  cars,  assumed  to  weigh  1200  Ibs.  per  lin.ft.,  whichever 
gives  the  larger  stress. 

115.  Traction  Force.     Viaduct  towers  and  similar  structures 
shall  be  designed  for  a  longitudinal  force,  applied  to  the  rail,  of 
20  per  cent,  of  the  live  load. 

1 1 6.  Centrifugal  Force.     Any  structure  located  on  a  curve 
shall  be  designed  to  resist  a  lateral  force  of  10  per  cent  of  the 
equivalent  live  load  per  lin.ft.,  applied  6  ft.  above  the  top  of 
rails.     (Par.   112.) 

UNIT  STRESSES 

117.  Structural    Steel.     All   parts   of   structures   shall   be   so 
proportioned  that  the  sum  of  the  maximum  stresses  shall  not 
exceed  for  structural  steel    and    rivet  steel  the  following  values 
in  Ibs.  per  sq.in.,  except  as  modified  in  Paragraphs  122  to  124. 

(a)  Axial  tension,  net  section 16,000  Ibs. 

(6)  Bending,  net  section,  on  extreme  fibers  of  rolled 

shapes,  built  sections,  and  plate  girders 16,000 

Pins,  on  extreme  fibers 24,000 

(c)  Axial  compression,   gross  section, 

S  -16000  -70- 
r 

where   S  =  allowable  unit  stress, 

/  =  unsupported  length  of  member  in  inches, 
r=  Least  radius  of  gyration  of  member  in  inches.     (Par. 
143.) 

(d)  Shear    on:  Turned  bolts  and  field  rivets,   when 

hand  driven 9,000  Ibs. 

Field  rivets,  when  power  driven 11,000 

Shop-driven  rivets  and  pins 12,000 

Plate  girder  webs,  gross  section 10,000 

(e)  Bearing  on:  Turned  bolts  and  field  rivets,  when 

hand  driven 18,000     " 

Field  rivets,  when  power  driven 22,000 

Shop-driven  rivets  and  pins 24,000 

Expansion  rollers,  perlin.in 600c/ 

where  d=  Diameter  of  roller  in  inches. 


RAILROAD  BRIDGES  29 

118.  Pressure  on  Foundations.     The    pressure    on    masonry 
foundations  shall  not   exceed  the  following  values    in  Ibs.   per 
square  inch: 

Portland  cement  concrete  1:2:4  and  first-class 
sandstone  or  limestone  masonry,  including 
impact 400  Ibs. 

Portland  cement  concrete  1 :2:0  (granitoid)  and 

first-class  granite  masonry,  including  impact  600  " 

119.  Pressure  on  Soils.     For  allowable  pressures  see  Par.  20. 

1 20.  Timber.     For  allowable  stresses  see  Part  VII. 

121.  Cast  Steel.     For  allowable  stresses  see  Par.  70. 

122.  Alternate    Stresses.      Members     subject     to     alternate 
stresses  of  tension  and  compression  shall  be  proportioned  for 
the  stress  giving  the  largest  section. 

If  alternate  stresses  occur  in  succession  during  the  passage 
of  one  train,  as  in  stiff  counters,  each  stress  shall  be  increased 
by  50  per  cent  of  the  smaller.  The  connections  shall  in  all  cases 
be  proportioned  for  the  sum  of  the  stresses. 

123.  Counter-Stresses.      Wherever    the   live-   and   dead-load 
stresses  are  of  opposite  character,  only  70  per  cent  of  the  dead- 
load  stress  shall  be  considered  as  effective  in  counteracting  the 
live-load  stress. 

124.  Combined    Stresses.     Members    subject    to    both    axial 
and  bending  stresses  shall  be  proportioned  so  that  the  combined 
fiber  stresses  will  not  exceed  the  specified  axial  stresses.     (Par. 
117.) 

For  stresses  produced  by  longitudinal  and  lateral  or  wind 
forces  combined  with  those  from  live  and  dead  load  and  cen- 
trifugal forces,  the  specified  unit  stresses  (Par.  117)  may  be 
increased  25  per  cent,  provided  that  this  combination  gives  a 
greater  sectional  area. 

DESIGN  OF  STRUCTURE. 

125.  General    Proportions.     The   width   between    centers    of 
trusses  shall  in  no  case  be   less  than   one-twentieth  (^)  of  the 
span,  nor  less  than  is  necessary  to  prevent  overturning  under 
the    assumed    lateral    loading. 

Trusses  shall  preferably  have  a  depth  of  not  less  than  one- 


30  STANDARD  SPECIFICATIONS 

tenth  (rro)  of  the  span.  Plate  girders  and  rolled  beams,  used 
as  girders,  shall  preferably  have  a  depth  of  not  less  than  one- 
twelfth  (jL)  of  the  span.  If  shallower  trusses,  girders,  or  beams 
be  used  the  section  shall  be  increased  so  that  the  maximum  deflec- 
tion will  not  be  greater  than  if  the  above  limiting  ratios  had  not 
been  exceeded. 

For  general  dimensions  see  Par.  75. 

126.  Floor  Framing.     Stringers   shall   preferably  be   riveted 
to  the  webs  of  all  intermediate  floor  beams  by  means  of  connection 
angles  not  less  than  ^  in.  thick.     Shelf  angles,  or  other  means 
provided  to  support  the  stringers  during  erection,  shall  not  be 
considered  as  carrying  any  of  the  reaction. 

Floor  beams  shall  preferably  be  arranged  so  as  to  be  perpendic- 
ular to  the  girder  or  truss  at  the  panel  point,  they  may  rest  upon 
the  top  chord  in  deck  bridges,  but  in  through  bridges  they  shall 
be  riveted  to  the  verticals. 

Where  end  floor  beams  are  not  used  stringers  resting  on 
masonry  shall  have  cross  frames  near  their  ends.  These  frames 
shall  be  riveted  to  girder  or  truss  shoes  where  practicable.  (Par. 
129.) 

127.  Beam  and  Plate-Girder  Bridges.     (See  Pars.  79,  125,  and 
Part  IV.) 

128.  Pony  Bridges.     Pony  trusses  shall  be  riveted  structures 
with  double-webbed   chords   and   shall  have   all    web  members 
latticed  or  otherwise  effectively  stiffened.     (Par.  80.) 

129.  Deck  Bridges.     Deck  spans  shall  have  transverse  brac- 
ing at  each  end  proportioned  to  carry  the  lateral  load  to  the 
supports.      (Par.  81.) 

130.  Through    Bridges.       All    trusses    shall    be    so    designed 
that  the  stresses  may  be  determined  with  reasonable  accuracy. 

The  hip  verticals  and  similar  members,  and  the  two  end  panels 
of  the  bottom  chords  of  all  single-track  pin-connected  trusses, 
and  of  all  double-track  trusses  over  300  ft.  span,  shall  be  made 
rigid. 

Rigid  counters  are  preferred,  and  where  subject  to  reversal 
of  stress  shall  preferably  have  riveted  connections  to  the  chords. 
Adjustable  counters  shall  have  open  turnbuckles. 

131.  Bracing.       Lateral,  longitudinal,  and  transveiv  bracing 
in  all  structures  shall  be  composed  of  rigid  members. 

Through  truss  spans  shall  have  riveted  portals  which  shall  be 


RAILROAD  BRIDGES  31 

rigidily  connected  to  the  end  posts  and  the  top  chords.  They 
shall  be  as  deep  as  the  clearance  will  permit. 

Intermediate  transverse  frames  shall  be  used  at  each  panel 
of  through  spans  having  vertical  truss  members  where  the 
clearance  will  permit. 

Lateral  bracing  shall  be  far  enough  below  the  flange  to  clear 
the  ties. 

The  minimum-sized  angle  to  be  used  in  lateral  bracing  shall 
be  34"X3"Xf".  Not  less  than  three  rivets  through  the  end  of 
the  angles  shall  be  used  at  the  connection. 

132.  Steel   Trestles.     The  struts  at  the  foot  of  trestle  towers 
shall  be  strong  enough  to  slide  the  movable  shoes  when  the  track 
is  unloaded.     (Par.  84.) 

133.  All    Structures.     Structures  shall  be  so  designed  that 
all  parts  w^ill  be  accessible  for  inspection,  cleaning,  and  painting. 

Pockets  or  depressions  which  would  hold  water  shall  have 
drain  holes,  or  be  filled  with  waterproof  material. 

DETAILS  OF  DESIGN 

134.  Minimum    Size  of  Material.     The  minimum  thickness 
of  metal,  except  for  fillers,  shall  be  f  in. 

Flanges  of  girders  or  built  members  without  cover  plate 
shall  have  a  minimum  thickness  of  one-twelfth  (^L)  of  the  width 
of  the  outstanding  leg.  (Par.  131.) 

135.  Details  of  Joints.     Main  members  of  trusses  shall  be 
so  arranged  around  the  joints  that  their  neutral  axes  will  be  as 
nearly  as  practicable  in  the  center  of  the  section  and  the  neutral 
axes  of  intersecting  main  members  shall  meet  in  a  common  point. 

Abutting  joints  in  compression  members  when  faced  for  bear- 
ing shall  be  spliced  on  four  sides  sufficiently  to  hold  the  connect- 
ing members  accurately  in  piace. 

All  other  joints  in  riveted  work,  whether  in  tension  or  in  com- 
pression, shall  be  fully  spliced. 

Where  splice  plates  are  not  in  direct  contact  with  the  parts 
which  they  connect  rivets  shall  be  used  on  each  side  of  the  joint 
in  excess  of  the  number  theoretically  required  to  the  extent  of 
one-third  (J)  of  the  number  for  each  intervening  plate. 

136.  Details   of   Connections.     The   strength   of   connections 
shall  be  sufficient  to  develop  the  full  strength  of  the  member, 


32  STANDARD  SPECIFICATIONS 

even  though  the  computed  stress  is  less,  the  kind  of  stress  to 
which  the  member  is  subjected  being  considered. 

137.  Riveted  Work.     (See  Par.  90.) 

138.  Rivets.     In  proportioning  rivets  their  nominal  diameter 
shall  be  used.     Rivets  shall  generally  be  |  in.  in  diameter,  and 
no    rivets,    except    in   lattice    bars,  shall  be  less  than  f  in.  in 
diameter. 

The  diameter  of  the  rivets  in  any  angle  carrying  a  calculated 
stress  shall  not  exceed  one-quarter  (J)  the  width  of  the  leg  through 
which  they  are  driven.  In  minor  parts  f-in.  rivets  may  be  used 
in  3-in.  angles  and  J-in.  rivets  in  2^-in.  angles. 

Rivets  carrying  a  calculated  stress  and  whose  grip  exceeds 
four  diameters  shall  be  increased  in  number,  at  least  1  per  cent 
for  each  additional  ^  in.  of  grip. 

Rivets  carrying  stress  and  passing  through  fillers  shall  be 
increased  50  per  cent  in  number,  and  the  excess  rivets,  when 
possible,  shall  be  outside  the  connected  member. 

Rivets  connecting  flanges  and  lattice  bars  shall  have  sizes 
as  follows:  f-in.  rivets  in  flanges  3^  in.  wide  and  over,  f-in.  rivets 
in  flanges  from  2^  to  3J  in.,  and  f-in.  rivets  in  flanges  less  than 
2J  in.  wide. 

139.  Rivet   Spacing.      The   minimum  distance   between  cen- 
ters of  rivet  holes  shall  be  three  diameters  of  the  rivet  and,  if 
possible,  not  less  than  3  in.  for  f-in.  rivets  and  2^  in.  for  f-in. 
rivets.     The  maximum  pitch,  in  the  direction  of  the  stress  for 
members  composed  of  plates  and   shapes,  shall  be  6  in.  for  f-in. 
rivets  and  5  in.  for  J-in.  rivets.      For  angles    with  two  gauge 
lines  and  rivets  staggered  the  maximum  shall  be  twice  the  above 
in  each  line. 

Where  two  or  more  plates  are  used  in  contact,  rivets  not  more 
than  12  in.  apart  in  either  direction  shall  be  used  to  hold  the 
plates  together. 

In  tension  members  composed  of  two  angles  in  contact  a  pitch 
of  12  in.  will  be  allowed  for  riveting  the  angles  together. 

The  maximum  pitch  at  ends  of  built-up  compression  mem- 
bers shall  not  exceed  four  diameters  of  the  rivet  for  a  length 
equal  to  two  times  the  width  of  the  members. 

140.  Edge     Distance    of    Rivets.      The     minimum    distance 
from  the  center  of  any  rivet  hole  to  a  sheared  edge  shall  be  1J  in. 
for  f-in.  rivets  and  1£  in.  for  J-in.  rivets,  and  to  a  rolled  edge 


RAILROAD  BRIDGES  33 

1J  in.  and  1£  in.  respectively.  The  maximum  distance  from 
any  edge  shall  be  eight  (8)  times  the  thickness  of  the  outside 
plate,  but  shall  not  exceed  5  in. 

141.  Tension  Members.     In  calculating  the  net  area  of  ten- 
sion members  the  area  of  rivet  holes  must  be  deducted,  assum- 
ing the  diameter  of  the  hole  to  be  J-  in.  larger  than  the  nominal 
size  of  the  rivet. 

Pin-connected  riveted  tension  members  shall  have  a  net 
section  through  the  pin  hole  25  per  cent  in  excess  of  that  through 
the  body  of  the  main  member.  The  minimum  net  section  back 
of  the  pin  hole,  parallel  to  the  axis  of  the  member,  shall  not  be 
less  than  that  through  the  body  of  the  main  member. 

142.  Eye-bars.     The  eye-bars  composing  a  member  shall  be 
so  arranged  that  adjacent  bars  shall  not  have  their  surfaces  in 
contact;  they  shall  be,  as  nearly  as  possible,  parallel  to  the  cen- 
tral plane  of  the  truss,  the  maximum  inclination  of  any  bar 
being  limited  to  1  inch  in  16  ft. 

Adjustable  eye-bars,  when  used  as  counters,  shall  have  the 
screw  ends  upset  and  shall  be  provided  with  turnbuckles,  or 
with  sleeve  nuts  provided  with  holes  drilled  through  two  opposite 
faces. 

143.  Compression  Members.     In  compression  members  form- 
ing chord  segments  as  much  as  possible  of  the  metal  shall  be 
concentrated  in  the  webs  and  flanges  and  the  neutral  axis  shall 
be  as  near  as  possible  to  the  center  of  the  web. 

In  all  compression  members  the  minimum  thickness  of  each 
single  web  plate  shall  be  one-thirty-second  (^)  of  the  distance 
between  the  inner  lines  of  rivets  connecting  it  to  the  flanges 
and,  when  two  or  more  plates  form  a  compound  web,  the  min- 
imum thickness  of  each  plate  shall  be  ^  in.  (Par.  139.) 

The  minimum  thickness  of  cover  plates  shall  be  one-fortieth 
(^)  of  the  distance  between  rivet  lines. 

No  compression  member  shall  have  a  length  exceeding  100 
times  its  least  radius  of  gyration,  except  those  used  for  wind 
and  lateral  bracing,  which  may  have  a  maximum  length  of  120 
times  their  least  radius  of  gyration. 

Forked  ends  on  compression  members  will  be  permitted  only 
where  unavoidable;  where  used  a  sufficient  number  of  pin  plates 
shall  be  provided  to  make  the  jaws  of  twice  the  sectional  area 
of  the  main  member.  At  least  one  of  these  plates  shall  extend 


34  STANDARD  SPECIFICATIONS 

to  the  far  edge  of  the  farthest  tie-plate  and  the  remainder  not 
less  than  6  in.  beyond  the  near  edge  of  the  same  plate. 

144.  Tie-plates.     The    open    sides   of    compression   members 
shall   be   stayed   by   diagonal  lattice   having  tie-plates   as  near 
each  end  as  practicable  and  at  intermediate  points  where  the 
lattice    is    interrupted.     In    main    members   the    end    tie-plates 
shall  have  a  length  not  less  than  the  distance  between  the  lines 
of  rivets  connecting  them  to  the  flanges,  and  intermediate  tie- 
plates  not  less  than  one-half  (J)  this  distance.     Their  thickness 
shall  not  be  less  than   one-forty-eighth   (£$)    of  the  same   dis- 
tance. 

145.  Lattice  Bars.     Single  lattice  bars  shall  have  an  inclina- 
tion of  approximately  60  degrees  with  the  axis  of  the  main  mem- 
ber and  shall  have  minimum  thickness  of  one-fortieth   (-fa)   of 
the  distance  between  the  rivets  connecting  them  to  the  member. 
Single  lattice  bars  may  be  connected  with  one  rivet,  except  in 
flanges  more  than  5  in.  wide,  where  two  rivets  shall  be  used. 

Double  lattice  bars  shall  be  used  where  the  distance  between 
rivet  lines  in  the  flanges  exceeds  15  in.  They  shall  have  a 
minimum  thickness  of  one-sixtieth  (-g^)  of  the  distance  between 
the  rivets  connecting  them  to  the  member,  shall  have  an  inclina- 
tion of  approximately  45  degrees,  and  shall  be  riveted  at  their 
intersection. 

Lattice  bars  shall  be  so  spaced  that  the  portion  of  the  flange 
included  between  their  connection  shall  be  as  strong  as  the 
member  as  a  whole. 

Instead  of  lattice  bars  shapes  of  equivalent  strength  may  be 
used  and  where  angles  are  used  they  shall  be  connected  by  at 
least  two  rivets. 

The  minimum  width  of  lattice  shall  be:  2J  in.  for  |-  in. -rivets, 
2\  in.  for  j  in. -rivets  and  2  in.  for  f  in. -rivets. 

146.  Pins.     The  minimum  diameter  of  pins  shall  be  eight- 
tenths  (•£$)  of  the  width  of  the  widest  eye-bar  attached  thereto. 

Members  shall  be  packed  on  pins,  using  filling  rings  where 
necessary,  in  a  manner  that  will  prevent  any  lateral  movement. 

Pins  shall  be  long  enough  to  insure  a  full  bearing  of  all  the 
parts  connected  upon  the  turned  body  of  the  pin.  They  shall 
be  secured  by  chamfered  nuts  or  be  provided  with  washers  if 
solid  nuts  are  used.  The  screw  ends  shall  be  long  enough  to 
admit  of  burring  the  threads. 


RAILROAD  BRIDGES  35 

147.  Pin    Holes.     Pin   holes   shall   be   reinforced   by   plates 
where  necessary,  and  at  least  one  plate  shall  be  as  wide  as  the 
flanges  will  allow  and  be  on  the  same  side  as  the  angles.     They 
shall  contain  sufficient  rivets  to  distribute  their  portion  of  the 
pin  pressure  to  the  full  cross-section  of  the  main  member. 

148.  Bolts.     Where    members    are    connected    by   bolts   the 
turned  body  of  these  shall   be  long  enough  to  extend    through 
the  metal.     A  washer  at  least  \  in.  thick  shall  be  used  under  the 
nut.     Bolts  shall  not  be  used  in  place  of  rivets  except  by  special 
permission.     Heads  and  nuts  shall  be  hexagonal. 

For  anchor  bolts  see  Par.  46. 

149.  Column  Bases  in  Trestles.     (See  Par.  101.) 

150.  Camber.     Ordinary  truss  spans  shall  be  given  a  camber 
by  making  the  panel  length  of  the  top  chords,  or  their  horizontal 
projections,  longer  than  the  corresponding  panels  of  the  bottom 
chord  in  the  proportion  of  £  in.  in  10  ft.     For  truss  spans  of 
unusual   length   or   loading,   draw   spans,   cantilevers,   etc.,   the 
camber  shall  be  obtained  from  the  calculated  distortion  of  the 
various  members  under  their  assumed  stress. 

151.  Bearings.     Bearing  plates  may  be  of  cast  steel  or  built 
up.     All  bearing  plates,  built-up  pedestals  and  built-up  bolsters 
or  shoes  shall  be  so  designed  and  set  upon  the  masonry  that  the 
load  will  be   distributed   over  the  entire  bearing  area  without 
causing  any  of  the  parts  to  be  overstressed. 

Movable  bearings  shall  be  designed  to  permit  motion  in  one 
direction  only;  fixed  bearings  shall  be  firmly  anchored  to  the 
masonry. 

Bridges  on  inclined  grade  without  pin  shoes  shall  have  the 
sole  plates  beveled  so  that  the  masonry  and  expansion  surfaces 
may  be  level. 

152.  Temperature.     Provision  shall  be  made  for  a  free  expan- 
sion  and    contraction    of    all   bridge    structures  to    the   extent 
of  £  inch  for  each  10  ft.  in  length.     Efficient  means  shall  be 
provided  to  prevent  excessive  motion  at  any  one  point. 

For  bridges  less  than  80  ft.  in  length  one  end  shall  be  free  to 
move  upon  smooth  surfaces. 

Bridges  of  80  ft.  and  over,  resting  on  masonry,  shall  have 
hinged  bolsters  or  shoes  at  both  ends.  At  one  end  the  shoes 
shall  rest  upon  a  nest  of  turned  expansion  rollers,  or  rockers  may 
be  used  for  the  same  purpose. 


36  STANDARD  SPECIFICATIONS 

Expansion  rollers  shall  not  be  less  than  4  in.  in  diameter. 
(Par.  117 e.)  They  shall  be  coupled  together  with  substantial  side 
bars  which  shall  be  so  arranged  that  the  rollers  can  be  readily 
cleaned.  (Par.  133.) 

In  very  high  trestle  towers  one  foot  shall  be  fixed,  two  feet 
shall  be  fixed  in  one  direction  only;  and  the  fourth  shall  be  free 
to  move  in  both  directions. 


PART  IV 

PLATE  GIRDERS 

153.  General  Requirements.     (See  Pars.  49-58  and  105-108.) 

154.  Loading.     The    loading    upon    plate    girders    shall    be 
taken,  when  used  in 

Buildings,  from  Pars.  1,  2  and  8-11; 
Highway  bridges,  from  Pars.  59-64;   and 
Railroad  bridges,  from  Pars.  109-116. 

155.  Unit  Stresses.     All  parts  of  plate  girders,  or  plate-girder 
bridges,  shall  be  so  proportioned  that  the  sum  of  the  maximum 
stresses  shall  not  exceed  for  structural  steel  and  rivet  steel  the 
following  values  in  pounds  per  square  inch,  except   as  modified 
in  Par.  124. 

(a)  Axial  tension,  net  section 16,000  Ibs. 

(b)  Bending,  net  section  of  tension  flange  (Par.  163) ...    16,000    " 

Pins,  on  extreme  fibers 24,000    " 

(c)  Axial  compression,  gross  section, 

S  =  16,000  -70-, 

where  S=  allowable  unit  stress, 

I  =  unsupported  length  of  member  in  inches  (Par.  167), 
r  =  least  radius  of  gyration  of  member  in  inches.     (Pars. 
39,  96  and  143.) 

(d)  Shear  on:  Turned  bolts  and  field  rivets,  when  hand 

driven ' 9,000  Ibs. 

Field  rivets,  when  power  driven 11,000    " 

Shop-driven  rivets  and  pins ....    12,000    " 

Webs  of  girder,  gross  section 10,000    " 

37 


38  STANDARD  SPECIFICATIONS 

(e)  Bearing  on.-  Turned  bolts  and  field  rivets  when 

hand  driven 18,000     " 

Field  rivets  when  power  driven .  22,000     " 

Shop-driven  rivets  and  pins 24,000     " 

Expansion  rollers,  per  lin.  inch 600d 

where    d=  diameter  of  roller  in  inches. 

(/)   For  girders  in  buildings  the  above  unit  stresses  for 
rivets  and  pins  shall  be  reduced  16f  per  cent. 
(g)   For  combined  stresses  see  Par.  124. 

For  allowable  unit  stresses  in  cast  steel  see  Par. 

70. 
For  allowable  pressures  on  walls  and  masonry 

foundations  see  Pars.   18  and  66. 
For  allowable  pressures  on  soils  see  Par.  20. 

156.  General    Proportions.     The    width    between    centers    of 
girders  in  deck  bridges,  carrying  a  single  straight  electric  railway 
or  railroad  track,  shall  generally  be  as  follows: 

For  spans  up    to    60  feet  inclusive   6'  6" 

"       "     from  60  feet  to  80     "  "         1'  0" 

"SO       "       and  over  7'  6" 

In  through  bridges  the  girders  shall  generally  be  spaced  so 
as  to  give  a  clear  width  of  10  ft.  at  the  top  of  rails  increasing  to 
14  ft.  at  a  height  of  4  ft.  above  same. 

For  additional  clearance  on  curves  see  Pars.  52  and  106. 

The  depth  of  plate  girders  in  buildings  shall  preferably  not 
be  less  than  one-sixteenth  (^)  of  the  span,  or  in  bridges  less 
than  one  twelfth  (-^)  of  the  span  and,  if  shallower  girders  be 
used,  the  section  be  increased  so  that  the  deflection  will  not  be 
greater  than  if  the  above  limiting  ratios  had  not  been  exceeded. 

For  general  dimensions  see   Par.   75. 

157.  Through    Bridges.     Through    plate    girders    shall    have 
their  top  flanges  stayed  at  each  end  of  every  floor  beam,  or  in 
case  of  solid  floors,  at  distances  not  exceeding  12  ft.,  by  knee 
braces  or  gusset  plates  stiffened  by  angles. 

Where  flooring  or  ties  are  supported  on  shelf  angles  riveted 
to  the  webs  of  the  girders  these  angles  shall  have  a  minimum 


PLATE  GIRDERS  39 

thickness  of  f  in.  and  shall  have  their  outstanding  leg  not  over 
3^  in.,  unless  they  are  supported  by  stiff eners  at  intervals  not 
over  30  in.  Such  shelf  angles  shall  not  be  considered  as  a  part  of 
the  flange. 

Through  plate  girders  shall  preferably  have  their  upper  corners 
neatly  rounded  off  to  a  radius  not  exceeding  3  ft.,  or  less  than 
one-third  (J)  of  the  depth  of  the  girder. 

Where  the  bridge  is  composed  of  two  or  more  spans  only  the 
corners  at  the  extreme  ends  need  be  rounded,  unless  the  girders 
vary  in  depth,  in  which  case  the  deeper  ones  shall  have  their  top 
flanges  rounded  to  meet  the  corner  of  the  adjacent  girder.  (Par. 
163.) 

158.  Skew   Bridges.     Ends    of    deck-plate    girders,    and    in 
through  bridges  ends  of  track  stringers  at  abutments,  shall  be 
square  to  the  track,  unless  a  ballasted  floor  be  used. 

159.  Design  of  Girder.     Plate  girders  shall  be  designed  either 
by  the  moment  of  inertia  of  their  net  section,  or  by  assuming  that 
the  flange  areas  are  concentrated  at  their  centers  of  gravity,  in 
which   case  one-eighth   (J)    of  the  gross   section  of  the  web,  if 
properly  spliced,  may  be  used  as  flange  section. 

160.  Design  of  Flanges.     In  girders  having  flange  plates  the 
total  flange  area  shall  be  so  divided  that  forty  per  cent  (40%) 
or  more  will  be  concentrated  in  the  flange  angles  and  side  plates, 
if  any,  and  the  remainder  in  the  cover  plates. 

Where  two  or  more  cover  plates  are  used  they  shall  be  of 
equal  thickness,  or  shall  decrease  in  thickness  outward  from 
the  angles. 

161.  Flange  Plates.     The  flange  plates  of  all  girders  shall  be 
limited  in  width,  so  as  not  to  extend  beyond  the  outer  lines  of 
rivets  connecting  them  to  the  angles  more  than  8  times  the  thick- 
ness of  the  outside  plate,  or  more  than  5  in.     (Par.  171.) 

All  cover  plates  shall  extend  at  each  end  at  least  12  in.  beyond 
the  points  where  they  might  be  cut  off  theoretically. 

162.  Flange    Splices.      Flange    splices,    where    unavoidable, 
shall  be  located  at  points  where  there  is  a  considerable  excess  of 
sectional  area.     Flange  angles  and  flange  plates  shall  all  break 
joints  so  that  no  two  pieces  will  be  spliced  within  18  in.  of  each 
other.     In  general  no  field  splices  will  be  allowed  in  girders  less 
than  70  feet  long;  this  provision,  however,  does  not  apply  to 
work  intended  for  export.      (Par.  135.) 


40  STANDARD  SPECIFICATIONS 

163.  Compression  Flange.     The  gross  section  of  the  compres- 
sion flange  shall  not  be  less  than  the  gross  section  of  the  tension 
flange.     The  unsupported  length   of  the   flange   shall   generally 
not  exceed  16  times  its  width  in  buildings,  or  12  times  its  width 
in  bridges. 

Where  the  unsupported  length  exceeds  these  ratios  the  flange 
shall  be  considered  as  a  column  between  the  points  of  sup- 
port. 

The  compression  flanges  of  girders  without  cover  plates  shall, 
in  buildings,  have  a  minimum  thickness  of  one-sixteenth  (^) 
of  the  width  of  the  outstanding  leg,  and  in  bridges  a  minimum 
thickness  of  one-twelfth  (-fa). 

In  bridges,  where  cover  plates  are  used,  one  plate  of  the  top 
flange  shall  extend  the  whole  length  of  the  girder.  In  through 
bridges  this  plate,  or  a  plate  of  the  same  width,  shall  be  extended 
over  the  rounded  corners  and  be  continued  down,  either  below 
the  corners  of  the  adjacent  girders,  or  at  the  extreme  ends  of  the 
bridges  down  to  the  bottom  of  the  girder.  (Par.  157.) 

164.  Flange  Rivets.     The   flanges  of   plate   girders   shall   be 
connected  to  the  web  with  a  sufficient  number  of  rivets  to  trans- 
fer the  calculated  shear  at  any  point,  in  a  distance  equal  to  the 
distance  between  centers  of  gravity  of  rivet  lines  at  that  point, 
combined  with  any  load  that  is  applied  directly  on  the  flange. 

The  wheel  loads,  where  rails  rest  directly  on  the  flange,  shall 
be  assumed  to  be  distributed  over  30  in.;  where  the  ties  rest  on 
the  flanges  the  wheel  loads  shall  be  assumed  to  be  distributed  over 
three  ties.  (Pars.  171,  283.) 

165.  Design  of  Web.     The  web  shall  be  designed  for  the  total 
maximum  shear,  assuming  this  to  be  uniformly  distributed  over 
its  gross  area. 

1 66.  Web   Splices.     When  necessary  to   splice  the  web  the 
splice  plates  and  the  number  of  rivets  shall  be  sufficient  to  resist 
the  maximum  stresses  resulting  from  a  combination  of  bending 
and  shear  at  that  point.      (Par.  171.) 

167.  Web  Stiffeners.     Web  stiffeners  shall  be  located  in  pairs 
at  the  ends  and  inner  edges  of  bearings  and  at  points  of  concen- 
trated loads,  their  area  to  be  determined  by  the  formula: 

S  =  16,000  -70-, 


PLATE  GIRDERS  41 


where   S  =  allowable  unit  stress. 

I  =  one-half  the  depth  of  girder  in  inches. 
r  =  Radius  of  gyration  of  angles,  neglecting  fillers  and 
inclosed  portion  of  web. 

End  stiffeners,  those  under  concentrated  loads  and  at  web  splices, 
shall  be  on  fillers  and  have  their  outstanding  legs  as  wide  as  the 
flange  angles  will  allow  and  shall  fit  tightly  against  them. 

Where  the  thickness  of  the  web  is  less  than  one-sixty-fourth 
(^)  of  its  depth  between  inner  rivet  lines  intermediate  stiffeners 
shall  be  used. 

The  intermediate  stiffeners  shall  be  spaced  by  the  formula: 

.  /16000X 
For  girders  in  buildings  t/<64n  —  ^  —  ). 


.  /12000X 
For  girders  in  bridges      «  <  64n  —  ^—  1  ; 

where  d=  distance  in  inches  between  centers  of  stiffeners,  with  a 
maximum  distance  equal  to  the  depth  of  the  girder,  or 
64  in. 

t  —  thickness  of  web  in  inches; 
Q  =  shear  in  web  per  square  inch. 

Intermediate  stiffeners  may  be  offset  (crimped),  and  their  out- 
standing legs  shall  not  be  less  than  one-thirty-second  (3^)  of  the 
depth  of  the  girder  plus  2  in. 

1  68.  Bracing.  All  deck-plate  girder  bridges  shall  have  lat- 
eral bracing  near  the  plane  of  the  top  chord,  but  far  enough 
below  the  flanges  to  clear  the  ties,  and  those  having  a  span  of 
60  ft.  or  over  shall  in  addition  have  lateral  bracing  in  the  plane 
of  the  bottom  chord.  Cross  frames  shall  be  located  near  each 
end  and  at  intermediate  points  not  exceeding  20  ft.  The  lateral 
system  shall  generally  be  of  the  single  cancellation  type. 

Through-plate  girder  spans,  not  having  a  solid  floor,  shall 
have  a  single  system  of  stringer  bracing  and  a  lateral,  double- 
intersection  system  of  bracing  in  the  plane  of  the  bottom  chord. 
All  bracing  shall  be  composed  of  rigid  members.  (Par  131.) 

169.  Minimum  Size  of  Material.  The  minimum  thickness 
of  metal,  except  for  fillers,  shall  be  for  girders  in  building  or 


42  STANDARD  SPECIFICATIONS 

highway  bridges  ^  in.  with  f-in.  rivets,  and  for  girders  in  railroad 
bridges  f  in.  with  f-in.  rivets. 

170.  Rivets.     In  proportioning  rivets  their  nominal  diameter 
shall  be  used.     The  diameter  of  the  rivets  in  any  angle  carrying 
a  calculated  stress  shall  not  exceed  one-quarter  (J)  the  width 
of  the  leg  through  which  they  are  driven.     Rivets  carrying  a 
calculated  stress  and  whose  grip  exceeds  four  diameters  shall 
be  increased  in  number,  at  least  one  per  cent  for  each  additional 

fg  in-  °f  grip. 

171.  Rivet    Spacing.     The    minimum  distance  between  cen- 
ters of  rivet  holes  shall  be  three  diameters  of  the  rivet  and,  if 
possible,  not  less  than  3  in.  for  f-in.  rivets  and  2J  in.  for  f-in. 
rivets.     In  the  flanges  the  maximum  pitch,  in  the  direction  of  the 
stress,  shall  be  6  in.  for  f-in.  rivets  and   5  in.    for  f-in.  rivets. 
For  angles  with  two  gauge  lines  and  rivets  staggered  the  maxi- 
mum  shall  be   twice  the  above  in  each  line.     Cover  plates  more 
than    16    in.    wide    shall  have  four  lines  of  rivets.     (Pars.   161 
and  164.) 

The  maximum  pitch  at  ends  of  cover  plates  shall  not  exceed 
four  diameters  of  the  rivet  for  a  length  equal  to  two  times  the 
width  of  the  plate. 

The  maximum  pich  in  stiffeners  shall  be  determined  by  the 
loading,  if  any,  but  shall  in  no  case  exceed  4J  in.  The  vertical 
web  splice  shall,  where  no  horizontal  plates  are  used,  have  at 
least  two  rows  of  rivets  on  each  side  of  the  joint  with  the  above 
maximum  pitch. 

172.  Edge  Distance.     (See  Par.  140.) 

173.  Bearings.     (See  Par.  151.) 

174.  Temperature.     (See  Par.  152.) 


PART  V 

MATERIALS  AND  WORKMANSHIP 


MATERIALS  FOR  STRUCTURAL  AND  RIVET  STEEL 

175.  Process  of  Manufacture.     Steel  shall  be  manufactured 
by  the  open-hearth  process. 

176.  Schedule  of  Requirements.     The  chemical  and  physical 
properties  shall  conform  to  the  following  limits,  except  as  modified 
in  Pars.  177  to  180.     The  yield  point,  as  indicated  by  the  drop 
of  beam,  shall  be  recorded  in  the  test  reports. 


Elements  Considered. 

Structural  Steel. 

Rivet  Steel. 

Cast  Steel. 

/  Basic 
Phosphorus,  max.  (  Acid 

Sulphur,  maximum  
Ultimate  tensile  strength  •> 
in    pounds  per  square    L 
inch*                          J 

0.04% 
0.06% 
0.05% 

Desired 
60,000 

0.04% 
0.04% 
0.04% 

Desired 
50,000 

0.05%   j    . 
0.08% 
0.05% 

Not  less  than 
65,000 

Flonp'atior)    min    %>  in  8 

l,500,000t 

1,500,000 

] 

i  in    Fie  3 

Ult.    tensile 

Ult.  tensile 

\        15% 

Elongation,  min.  in  2  in.,  \ 
Fig  4                    / 

strength 

22% 

strength 

J 

Character  of  fracture  
Cold  bends  without  frac-  \ 
•  ture  / 

silky 
180°  flatj 

silky       -| 
180°  flat§ 

silky    or    fine 
granular, 
in  90°,  d  =  3 

177.*  Allowable  Variations.  If  the  ultimate  strength  varies 
more  than  4000  Ibs.  from  that  desired  a  retest  shall  be  made 
on  the  same  gauge,  which,  to  be  acceptable,  shall  be  within  5000 
Ibs.  of  the  desired  ultimate. 

178.1  Modification  in  Elongation.  For  material  less  than 
^  in.  and  more  than  J  in.  in  thickness  the  following  modifica- 
tions will  be  allowed  in  the  requirements  for  elongation : 

43 


44  STANDARD  SPECIFICATIONS 

(a)  For  each  ^  inch  in  thickness  below  ^  in.  a  deduction 
of  2^  will  be  allowed  from  the  specified  percentage. 

(6)  For  each  J  in.  in  thickness  above  f  in.  a  deduction  of 
1  will  be  allowed  from  the  specified  percentage. 

I7Q.J  Bending  Tests.  Bending  tests  may  be  made  by 
pressure  or  by  blows.  Plates,  shapes,  and  bars  less  than  1  in. 
thick  shall  bend  as  called  for  in  Par.  176. 

Full-sized  material  for  eye-bars  and  other  steel  1  in.  thick 
and  over,  tested  as  rolled,  shall  bend  cold  180  degrees  around  a 
pin,  the  diameter  of  which  is  equal  to  twice  the  thickness  of 
the  bar,  without  any  fracture  on  the  outside  of  bend. 

Angles  J  in.  and  less  in  thickness  shall  open  flat,  and  angles 
-J  in.  and  less  in  thickness  shall  bend  shut,  when  cold,  under 
blows  of  a  hammer,  without  sign  of  fracture.  This  test  will  be 
made  only  when  required  by  the  inspector. 

i8o.§  Nicked  Bends.  Rivet  steel,  when  nicked  and  bent 
around  a  bar  of  the  same  diameter  of  the  rivet  rod,  shall  give 
a  gradual  break  and  a  fine,  silky,  uniform  fracture. 

181.  Chemical    Analyses.     Chemical   determinations   of    the 
percentages  of  carbon,  phosphorus,  sulphur  and  manganese  shall 
be  made  by  the  manufacturer  from  a  test  ingot  taken  at  the  time 
of  the  pouring  of  each  melt  of  steel  and  a  correct  copy  of  such 
analysis  shall  be  furnished  to  the  Engineer  or  his  inspector.    Check 
analyses  shall  be  made  from  finished  material,  if  called  for  by  the 
purchaser,  in  which  case  an  excess  of  25  per  cent,   above  the 
required  limits  will  be  allowed. 

182.  Form  of  Specimens. 

(«)  Plates,  Shapes  and  Bars:  Specimens  for  tensile  and 
bending  tests  for  plates,  shapes  and  bars  shall  be  made 


-rAliont 

"'-        03' 

Parallel  Section 
not  less  than  9" 

\y." 

^^^^_ 

^^^^~ 

't 

*     *     *  . 

I 

S^~ 

^"^x 

V 

-  *&f  8  Spaces   fi)  l"  *ti< 

Uf —  — -About  18/z—  — =H 

FIG.  3. 

by  cutting  coupons  from  the  finished  product,  which 


MATERIALS  AND  WORKMANSHIP 


45 


shall  have  both  faces  rolled  and  both  edges  milled  to 
the  form  shown  by  Fig.  3;  or  with  both  edges  parallel; 
or  they  may  be  turned  to  a  diameter  of  }  in.  for  a  length 
of  at  least  9  in.  with  enlarged  ends. 

(b)  Rivets:    Rivet  rods  shall  be  tested  as  rolled. 

(c)  Pins  and  Rollers :     Specimens  shall  be  cut  from  the  finished 

rolled  or  forged  bar,  in  such  a  manner  that  the  center 
of  the  specimen  shall  be  1  in.  from  the  surface  of  the 
bar.  The  specimen  for  tensile  test  shall  be  turned  to 


l^ 

4X" 

1 

<  — 

K/\\*V 

-X----3 

\\N\\\ 

W> 

J 

<  —                         —25^^— 

N. 

\\ 

f| 

11 

^                                                                             *         J 

• 

1 

• 

1 

A 

*       *f 

, 

/  A 

wyW/ 

3x' 

_                                    „//                                    Jl 

3*'"^. 

v' 

FIG.  4. 


the  form  shown  in  Fig.  4.     The  specimen  for  bending 
test  shall  be  1  in.  by  ^  in.  in  section. 

(d)  Cast  Steel.  The  number  of  tests  will  depend  on  the 
character  and  importance  of  the  castings.  Specimen 
shall  be  cut  cold  from  cupons  molded  and  cast  on-  some 
portion  of  one  or  more  castings  from  each  melt  or  from 
the  sink  heads,  if  the  heads  are  of  sufficient  size.  The 
coupon  or  sink  head,  so  used,  shall  be  annealed  with  the 
casting  before  it  is  cut  off.  Test  specimens  to  be  of  the 
form  prescribed  for  pins  and  rollers. 

183.  Annealed    Specimens.     Material    which   is    to    be    used 
without  annealing  or  further  treatment  shall  be  tested  in  the 
condition  in  which  it  comes  from  the  rolls.     When  material  is 
to  be  annealed,  or  otherwise  treated  before  use,  the  specimens 
for  tensile  tests  representing  such  material  shall  be  cut  from  prop- 
erly annealed  or  similarly  treated  short  lengths  of  the  full  section 
of  the  bar. 

184.  Number  of  Tests.     At  least  one  tensile  and  one  bending 
test  shall  be  made  from  each  melt  of  steel  as  rolled.     In  case 


46  STANDARD  SPECIFICATIONS 

steel  differing  f  in.  and  more  in  thickness  is  rolled  from  one  melt 
a  test  shall  be  made  from  the  thickest  and  thinnest  material 
rolled. 

185.  Finish.     Finished  material  shall  be  free  from  injurious 
seams,  flaws,  cracks,  defective  edges,  or  other  defects,  and  have 
a  smooth,   uniform,  and   workmanlike  finish.     Plates  36  in.   in 
width  and  under  shall  have  rolled  edges. 

1 86.  Stamping.      Every   finished   piece    of   steel   shall   have 
the  melt  number  and  the  name  of  the  manufacturer  stamped 
or  rolled  upon  it.      Steel  for  pins  and  rollers  shall  be  stamped 
on   the   end.      Rivet   and   lattice   steel    and   other    small   parts 
may  be   bundled  with   the  above  marks  on  an  attached  metal 
tag. 

187.  Defective  Material.     Material  which,  subsequent  to  the 
above  tests  at  the  mills,  and  its  acceptance  there,  develops  weak 
spots,  brittleness,  cracks  or  other  imperfections,  or  is  found  to 
have  injurious  defects,  will  be  rejected  at  the  shop  and  shall  be 
replaced  by  the  manufacturer  at  His  own  cost. 

188.  Allowable  Variation  in  Weight  (when  ordered  to  weight). 
A  variation  in  cross-section  or  weight  of  each  piece  of  steel  of 
more  than  2J  per  cent  from  that  specified  will  be  sufficient  cause 
for  rejection,   except  in   case  of  sheared  plates,  which  will  be 
covered  by  the  following  permissible  variations  applying  to  single 
plates  only:  Plates  under  12^  Ibs.  per  sq.ft. 

(a)  Up  to  75  in.  wide,  2^  per  cent  above  and  below  the  pre- 
scribed weight. 

(6)  75  in.  and  up  to  100  in.  wide,  5  per  cent  above  or  3  per 
cent  below. 

(c)  100  in.  wide  and  over,  10  per  cent  above  or  3  per  cent 

below. 
Plates  12^  Ibs.  per  sq.ft.  or  heavier. 

(d)  Up  to  100  in.,  2^  per  cent  above  or  below. 

(e)  100  in.  wide  and  over,  5  per  cent  above  or  below. 

189.  Allowable  Variation  in  Weight  (when  ordered  to  gauge). 
Plates  will  be  accepted  if  they  do  not  measure  more  than  0.01 
in.  below  the  ordered  thickness. 

An  excess  over  the  nominal  weight,  corresponding  to  the 
dimensions  on  the  order,  will  be  allowed  for  each  plate,  if  not 
more  than  that  shown  in  the  following  table,  one  cubic  inch  of 
rolled  steel  being  assumed  to  weigh  0.2833  Ib. 


MATERIALS  AND  WORKMANSHIP 


47 


Thickness 

Nominal 

Width  of  Plate. 

Inch. 

Pounds. 

Up  to  75". 

75"  and  up 
to  100". 

100"  and  up 
to  115". 

Over  115". 

. 

J 

10.20 

10% 

14   % 

18  % 

& 

12.75 

8  % 

12  % 

16  % 

I 

15.30 

7  % 

10  % 

13  % 

17% 

r 

17.85 
20.40 

6  % 
5  % 

8  % 
7  % 

10  % 

9  % 

13% 
12% 

& 

22.95 

4*% 

6*% 

8*% 

11% 

i 

25.50 

4% 

6  %     - 

8  % 

10% 

over  | 

3}% 

5  % 

64% 

9% 

190.  Cast  Iron.     Except  where  chilled  iron  is  specified,  cast- 
ings shall  be  made  of  tough  gray  iron,  with  sulphur  not  over 
0.10  per  cent.     They  shall  be  true  to  pattern,  out  of  wind  and 
free  from  flaws  and  excessive  shrinkage.     If  tests  be  demanded 
the}-  shall  be  made  on  the  "Arbitration  Bar  "  of  the  American 
Society  for  Testing  Materials,  which  is  a  round  bar  1£  in.  in  diam- 
eter and  15  inches  long.     The  transverse  test  shall  be  made  on  a 
supported  length  of  12  in.  with  a  load  at  middle.     The  minimum 
breaking  load  so  applied  shall  be  2900  Ibs.  with  a  deflection  of 
at  least  yff  in.  before  rupture. 

191.  Wrought-Iron   Bars.      Wrought    iron   shall    be   double 
rolled,   tough,   fibrous,  and  uniform  in   character.     It   shall  be 
thoroughly  welded  in  rolling  and  be  free  from  surface  defects. 
When  tested  in  specimens  of  the  form  of  Fig.  3,  or  in  full-sized 
pieces  of  the  same  length,  it  shall  show  an  ultimate  strength  of 
at  least  50,000  Ibs.  per  sq.in.,  an  elongation  of  at  least  18  per 
cent  in  8  inches,  with  fracture  wholly  fibrous.     Specimens  shall 
bend  cold,  with  the  fiber,  through  135  degrees,  without  sign  of 
fracture,  around  a  pin  the  diameter  of  which  is  not  over  twice 
the  thickness  of  the  piece  tested.     When  nicked  and  bent,  the 
fracture  shall  show  at  least  90  per  cent  fibrous. 

MATERIALS  FOR  CONCRETE  REINFORCEMENT  BARS* 

192.  Process  of  Manufacture.     Steel  may  be  made  by  either 
the  open-hearth  or  Bessemer  process.     Bars  shall  be  rolled  from 
billets. 


*  As  adopted  by  The  Association  of  American  Steel  Manufacturers,  1910. 


48 


STANDARD  SPECIFICATIONS 


193.  Schedule  of  Requirements.     The  chemical  and  physical 
properties  shall  conform  to  the  following  limits: 


Structural-Steel  Grade. 

Hard-Steel  Grade. 

Cold- 

Elements  Considered. 

twisted 

Plain 

Deformed 

Plain 

Deformed 

Bars. 

Bars. 

Bars. 

Bars. 

Bars. 

Phosphorus,  /  Bessemer  
max.           \  Open-hearth  .  . 

0.10% 
0.06% 

0.10% 
0.06% 

0.10% 
0.06% 

0.10% 
0.06% 

0  .  10% 
0.06% 

Ultimate    tensile    strength,  J 

55.000  to 

55,000  to    80,000  mi 

80,000  min. 

Recorded 

Ibs.  per  sq.in. 

70,000 

70,000 

only 

Yield  point,  minimum,  Ibs.  / 
per  sq.in. 

33,000 

33,000 

50,000 

50,000 

55,000 

f 

1,400,000 

1,250,000 

1,200.000 

1,000,000. 

5% 

.fcjlongation  min  per  cent  in   ' 

8  inches  '                                 \ 

Ult.  tensile 

Ult.  tensile 

Ult.  tensile 

Ult.  tensile 

Cold  bends  without  fracture: 

strength 

strength 

strength 

strength 

Bars  under  f  "  in.  diam.  or  1 
thickness 

180°rf  =  <       180°,  d  =  t 

180°,  d  =  3t 

180°,  d  =  4* 

180°,  d  =  2t 

Bars  %"  in.  diam.  or  thick-  \ 
ness  and  over                    / 

lSO°,d=t 

180°,  d  =  2t 

90°,  d  =  3t 

90°,  d  =  4t 

180°,  d  =  3« 

The  hard-steel  grade  will  be  used  only  when  specified. 

194.  Chemical   Determinations.     In    order    to    determine    if 
the  material  conforms  to  the  chemical  limitations  prescribed  in 
Par.   193,  analysis  shall  be  made  by  the  manufacturer  from  a 
test  ingot  taken  at  the  time  of  the  pouring  of  each  melt  or  blow 
of  steel,  and  a  correct  copy  of  such  analysis  shall  be  furnished 
to  the  engineer  or  his  inspector. 

195.  Yield    Point.     For  the  purpose  of  these   specifications, 
the  yield  point  shall  be  determined  by  careful  observation  of  the 
drop  of  the  beam  of  the  testing  machine,  or  by  other  equally 
accurate  methods. 

196.  Form  of  Specimens. 

(a)  Tensile  and  bending-test  specimens  may  be  cut  from 
the  bars  as  rolled,  but  tensile  and  bending-test  specimens 
of  deformed  bars  may  be  planed  or  turned  for  a  length 
of  at  least  9  in.  if  deemed  necessary  by  the  manufacturer 
in  order  to  obtain  uniform  cross-section. 

(6)  Tensile  and  bending-test  specimens  of  cold-twisted  bars 
shall  be  cut  from  the  bars  after  twisting,  and  shall  be 
tested  in  full  size  without  further  treatment,  unless 
otherwise  specified  as  in  (c) ,  in  which  case  the  conditions 
therein  stipulated  shall  govern. 

(c)  If  it  is  desired  that  the  testing  and  acceptance  for  cold- 
twisted  bars  be  made  upon  the  hot-rolled  bars  before 


MATERIALS  AND  WORKMANSHIP  49 

being  twisted,  the  hot-rolled  bars  shall  meet  the  require- 
ments of  the  structural-steel  grade  for  plain  bars  shown 
in  this  specification. 

197.  Number  of  Tests.     At  least  one  tensile  and  one  bending 
test  shall  be  made  from  each  melt  of  open-hearth  steel  rolled, 
and  from  each  blow  or  lot  of  ten  tons  of  Bessemer  steel  rolled. 
In  case  bars  differing  f  in.  and  more  in  diameter  or  thickness 
are  rolled  from  one  melt  or  blow,  a  test  shall  be  made  from  the 
thickest  and  thinnest  material  rolled.     Should  either  of  these  test 
specimens   develop    flaws,   or   should    the  tensile-test   specimen 
break  outside  of  the  middle  third  of  its  gauged  length,  it  may 
be   discarded   and   another  test   specimen   substituted   therefor. 
In  case  a  tensile-test  specimen  does  not  meet  the  specifications, 
an  additional  test  may  be  made. 

The  bending  test  may  be  made  by  pressure  or  by  light  blows. 

198.  Modifications  in  Elongation  for  Thin  and  Thick  Material. 
For  bars  less  than  ^  in.  and  more  than  f  in.  nominal  diameter 
or  thickness,  the  following  modifications  shall  be  made  in  the 
requirements  for  elongations: 

(a)  For  each  increase  of  J  in.  in  diameter  or  thickness  above 

f  in.,  a  deduction  of  one  shall  be  made  from  the  specified 
percentage  of  elongation. 

(b)  For  each  decrease  of  ^  inch  in  diameter  or  thickness 

below  ^  in.,  a  deduction  of  one  shall  be  made  from  the 
specified  percentage  of  elongation. 

(c)  The  above  modifications  in  elongation  shall  not  apply 

to  cold-twisted  bars. 

199.  Number  of  Twists.     Cold-twisted  bars  shall  be  twisted 
cold  with  one  complete  twist  in  a  length  equal  to  not  more  than 
12  times  the  thickness  of  the  bar. 

200.  Finish.     Material   must   be   free   from  injurious   seams, 
flaws,  or  cracks,  and  have  a  workmanlike  finish. 

201.  Variation  in  Weight.     Bars  for  reinforcement  are  subject 
to  rejection  if  the  actual  weight  of  any  lot  varies  more  than  5 
per  cent  over  or  under  the  theoretical  weight  of  that  lot. 

WORKMANSHIP 

202.  General.     All  parts  forming  a  structure   shall  be  built 
in  accordance  with  approved  drawings.      The  workmanship  and 
finish  shall  be  equal  to  the  best  practice  in  modern  bridge  works. 


50  STANDARD  SPECIFICATIONS 

203.  Straightening  Material.     Material    shall    be   thoroughly 
straightened  in  the  shop  by  methods  that  will  not  injure  it,  before 
being  laid  off  or  worked  in  any  way. 

The  several  pieces  forming  one  built  member  shall  be  straight 
and  fit  closely  together,  and  finished  members  shall  be  free  from 
twists,  bends  or  open  joints. 

204.  Lattice    Bars.     Lattice  bars  shall  have  neatly  rounded 
ends,  unless  otherwise  called  for. 

205.  Finish.     Shearing  shall  be  neatly  and  accurately  done 
and  all  portions  of  the  work  exposed  to  view  neatly  finished  with 
sharp  cutting  tools,  a  chisel,  or  a  file. 

206.  Edge  Planing.     In  all  material  over  -|  in.  thick  the  sheared 
edges  or  ends  shall  be  planed  at  least  J  in. 

207.  Finish  of  Joints.     Abutting  joints  shall  be  cut  or  dressed 
true  and  straight  and  fitted  close  together,  especially  where  open 
to  view.     In  compression  joints,  depending  on  contact  bearing, 
the  surfaces  shall  be  truly  faced,  so  as  to  have  even  bearings 
after  they  are  riveted  up  complete  and  when  perfectly  aligned. 

208.  Field  Connections.     Holes  for  floor  beam  and  stringer 
connections  shall  be  sub-punched  and  reamed  according  to  Par. 
212  to  a  steel  templet  one  inch  thick. 

All  other  field  connections,  except  those  for  laterals  and  sway 
bracing,  shall  be  assembled  in  the  shop  and  the  unfair  holes 
reamed;  and  when  so  reamed  the  pieces  shall  be  match-marked 
before  being  taken  apart. 

209.  Connection  Angles.     Connection  angles  for  floor  beams, 
stringers,   and  plate  girders  shall  be  flush  with  each  other  and 
correct  as  to  position  and  length  of  girder. 

When  not  correct  after  being  riveted  up  milling  will  be  required 
and  the  removal  of  more  than  £$  in.  from  their  thickness  will  be 
cause  for  rejection. 

210.  Rivet  Holes.     When  reaming  is  not  required  the  diameter 
of  the  punch,  shall  not   be   more  than   ^  in.  greater  than  the 
diameter   of  the   rivet;  nor  the  diameter  of  the  die  more  than 
J    in.    greater   than  the   diameter    of    the   punch.      (Pars.    212 
and  214.) 

211.  Punching.    All  punching  shall  be  accurately  done.    Drift- 
ing to  enlarge  unfair  holes  will  not  be  allowed.     If  the  holes  must 
be  enlarged  to   admit  the  rivet,  they   shall  be  reamed.     Poor 
matching  of  holes  will  be  cause  for  rejection.     (Par.  212.) 


MATERIALS  AXD  WORKMAXSHIP  51 

212.  Sub-punching  and  Reaming.     All  material  more  than 
-f  in.  thick  shall  be  sub-punched  and  reamed  or  drilled  from  the 
solid. 

When  reaming  is  required  the  punch  used  shall  have  a  diameter 
not  less  than  J  in.  smaller  than  the  nominal  diameter  of  the  rivet. 
Holes  shall  then  be  reamed  to  a  diameter  not  more  than  ^  in. 
larger  than  the  nominal  diameter  of  the  rivet.  All  reaming  shall 
be  done  with  twist  drills.  (Pars.  208,  213.) 

213.  Burrs.     The    outside   burrs   on   reamed   holes   shall   be 
removed. 

214.  Reaming  after  Assembling.*     When  general  reaming  is 
required  it  shall  be  done  after  the  pieces  forming  one  built  mem- 
ber are  assembled  and  firmly  bolted  together.     If  necessary  to  take 
the  pieces  apart  for  shipping  and  handling  the  respective  pieces 
reamed  together  shall  be  so  marked  that  they  may  be  reassembled 
in  the  same  position  in  the  final  setting  up.     No  interchange  of 
reamed  parts  will  be  allowed. 

215.  Size  of   Rivets.     The  size  of  rivets,  called  for  on  the 
plans,  shall  be  understood  to  mean  the  actual  size  of  the  cold 
rivet  before  heating. 

216.  Rivets.      Rivets    shall     be     driven    by    pressure    tools 
wherever  possible.     Pneumatic  hammers  shall  be  used  in  prefer- 
ence to  hand  driving. 

217.  Field    Rivets.     Field   rivets   shall   be   furnished   to   the 
amount  of  15  per  cent  plus  ten  rivets  in  excess  of  the  nominal 
number  required  for  each  size. 

218.  Turned  Bolts.     Wherever   bolts   are   used   in   place   of 
rivets  which  transmit  shears  the  holes  shall  be  reamed  parallel 
and  the  bolts  turned  to  a  driving  fit.     A  washer  not  less  than  ^ 
in.  thick  shall  be  used  under  the  nut. 

219.  Riveting.     Rivets    shall    look    neat    and    finished    with 
heads  of  approved  shape,  full  and  of  equal  size.     They  shall  be 
central  on  shank  and  grip  the  assembled  pieces  firmly.     Recup- 
ping  and  caulking  will  not  be  allowed.     Loose,  burned,  or  other- 
wise defective  rivets  shall  be  cut  out  and  replaced.     In  cutting 
out  rivets  great  care  shall  be  taken  not  to  injure  the  adjacent 
metal.     If  necessary  they  shall  be  drilled  out. 

*  This  paragraph  contains  a  special  requirement  which,  to  be  valid  under 
these  specifications,  shall  be  specifically  mentioned  in  the  contract  between 
the  purchaser  and  the  manufacturer. 


52  STANDARD  SPECIFICATIONS 

220.  Assembling.     Riveted,  members  shall  have  all  parts  well 
pinned  up  and  firmly  drawn  together  with  bolts  before  riveting 
is  commenced.     Contact  surfaces  to  be  painted.     (Par.  250.) 

221.  Web  Plates.     In  buildings  web  plates  of  girders  shall 
not  be  recessed  from  the  backs  of  angles  more  than  J  in. 

In  bridges  web  plates  of  girders  which  have  no  cover  plates 
shall  be  flush  with  the  backs  of  angles  or  shall,  in  the  top  chord, 
project  above  the  same  not  more  than  J  in.  unless  otherwise 
called  for. 

When  web  plates  are  spliced  not  more  than  J  in.  clearance 
between  ends  of  plates  will  be  allowed. 

222.  Splice  Plates  and  Fillers.     Web  splice  plates  and  fillers 
under  stiffeners  shall  be  cut  to  fit  within  J  in.  of  flange  angles. 

223.  Web    Stiffeners.     Stiffeners    shall    fit    neatly    between 
flanges  of  girders.     Where  tight  fits  are  called  for  the  ends  of 
stiffeners  shall  be  faced  and  shall  be  brought  to  a  true  contact 
bearing  with  the  flange  angles. 

224.  Eye-Bars.     Eye-bars  shall  be  straight  and  true  to  size 
and  shall  be  free  from  twists,  folds  in  the  neck  or  head,  or  any 
other  rlefect. 

Heads  shall  be  made  by  upsetting,  rolling,  or  forging.  Welding 
will  not  be  allowed.  The  form  of  heads  will  be  determined  by 
the  dies  in  use  at  the  works  where  the  eye-bars  are  made,  if 
satisfactory  to  the  engineer,  but  the  manufacturer  shall  guarantee 
the  bars  to  break  in  the  body  when  tested  to  rupture.  The 
thickness  of  head  and  neck  shall  not  vary  more  than  ^  in. 
from  that  specified.  (Par.  248.) 

225.  Boring     Eye-Bars.     Before    boring    each    eye-bar  shall 
be    properly    annealed    and    carefully    straightened.     Pin  holes 
shall  be  in  the  center  line  of  bars  and  in  the  center  of  heads. 
Bars  of  the  same  length  shall  be  bored  so  accurately  that,  when 
placed   together,  pins  ^  in.  smaller  in  diameter   than  the    pin 
holes  can  be  passed  through  the  holes  at  both  ends  of  the  bars 
at  the  same  time  without  forcing. 

226.  Pin  Holes.     Pin-holes    shall    be    bored  true  to  gauges, 
smooth  and  straight;    at  right  angles  to  the  axis  of  the  member 
and   parallel   to   each   other,   unless   otherwise   called   for.     The 
boring  shall  be  done  after  the  member  is  riveted  up. 

227.  Variation  in  Pin  Holes.     The  distance  center  to  center 
of  pin  holes  shall  be  correct  within  ^  in.  and   the  diameter  of 


MATERIALS  AND  WORKMANSHIP  53 

the  holes  not  more  than  -fa  in.  larger  than  that  of  the  pin,  for 
pins  up  to  o  in.  diameter,  and  ^  in.  for  larger  pins. 

228.  Pins  and  Rollers.     Pins  and  rollers  shall  be  acurately 
turned  to  gauges  and  shal   be  straight  and  smooth  and  entirely 
free  from  flaws. 

229.  Pilot  Nuts.     Pilot  and   driving  nuts  shall  be  furnished 
for  each  size  of  pin  in  such  numbers  as  may  be  ordered. 

230.  Screw   Threads.     Screw  threads   shall   make   tight   fits 
in  the  nuts  and  shall  be  U.S.  standard,  except  above  the  diameter 
of  If  in.,  when  they  shall  be  made  with  six  threads  per  inch. 

231.  Bed  Plates.     Expansion  bed  plates  and    vertical  webs 
of  pedestals  shall  be  planed  true   and   smooth.     Cast  wall   or 
bed  plates  shall  be  planed  top  and  bottom.     The  cut  of  the  plan- 
ing tool  shall  correspond  with  the  direction  of  expansion. 

232.  Annealing.     Steel,  except  in  minor  details,  which  has 
been  partially  heated  shall  be  properly  annealed.     (Par.  233.) 

233.  Steel  Castings.     All  steel  castings  shall  be  annealed. 

234.  Welds.     Welds  in  steel  will  not  be  allowed. 

235.  Shipping  Details.     Pins,   nuts,   bolts,   rivets,  and   other 
small  details  shall  be  boxed  or  crated. 

236.  Weight.     The    weight    of    every    piece    and    box    shall 
be  marked  on  it  in  plain  figures. 

237.  Finished  Weight.     Payment  for  pound  price  contracts 
shall  be  by  scale  weight.     No  allowance  over  2  per  cent  of  the 
total  weight  of  the  structure,  as  computed  from  the  plans,  will 
be  made  for  excess  weight. 


PART  TI 

INSPECTION,   PAINTING,   AND  ERECTION 

INSPECTION  AND  TESTING 

238.  Copies  of  Mill  Orders.     The  purchaser  shall  be  furnished 
copies  of  mill  orders  and  no  material  shall  be  rolled,  or  work 
done,  before  the  purchaser  has  been  notified  where  the  orders 
have  been  placed,  so  that  he  may  arrange  for  the  inspection. 

239.  Facilities  for  Mill  Inspection.     The  manufacturer  shall 
furnish  all  facilities  for  inspecting  and  testing  the  weight  and 
quality  of  all  material  at  the  mill  where  it  is  manufactured. 
He  shall  furnish  a  suitable  testing  machine  for  testing  the  spec- 
imens, as  well  as  prepare  the  pieces  for  the  machine,  free  of  cost. 

240.  Access  to  Mills.     When  an  inspector  is  employed  by 
the  purchaser  to  inspect  material  at  the  mills,  he  shall  have 
full  access,  at  all  times,  to  all  parts  of  mills  where  material  to 
be  inspected  by  him  is  being  manufactured. 

241.  Facilities  for  Shop  Inspection.     The   manufacturer  shall 
furnish  all  facilities  for  inspecting  and  testing  the  weight  and 
quality  of  workmanship   at  the  shop  where  material  is  manu- 
factured.    He  shall  furnish  a  suitable  testing  machine  for  testing 
full-sized  members,  if  required. 

242.  Starting  Work  in  Shops.     The  purchaser  shall  be  noti- 
fied well  in  advance  of  the  start  of  the  work  in  the  shop  in  order 
that  he  may  have  an  inspector  on  hand  to  inspect  material  and 
workmanship. 

243.  Access  to   Shop.     When   an  inspector  is  employed   by 
the  purchaser  he  shall  have  full  access,  at  all  times,  to  all  parts 
of  the  shop  where  material  under  his  inspection  is  being  manu- 
factured. 

244.  Accepting    Material    or    Work.     The    inspector    shall 
stamp   each  piece   accepted   with   a  private   mark.     Any   piece 
not  so  marked  may  be  rejected  at  any  time  and  at  any  stage  of 

54 


INSPECTION^  PAINTING,  AND  ERECTION  55 

the  work.  If  the  inspector,  through  an  oversight  or  otherwise, 
has  accepted  material  or  work  which  is  defective  or  contrary 
to  the  specifications,  this  material,  no  matter  in  what  stage  of 
completion,  may  be  rejected  by  the  purchaser. 

245.  Shop  Plans.     The  purchaser  shall  be  furnished  complete 
shop  plans. 

246.  Shipping  Invoices.     Complete  copies  of  shipping  invoices 
shall  be  furnished  to  the  purchaser  with  each  shipment. 

247.  Test  to  Prove  Workmanship.     Full-sized  tests  on  eye- 
bars  and  similar  members,  to  prove  the  workmanship,  shall  be 
made  at  the  manufacturer's  expense  and  shall  be  paid  for  by 
the  purchaser  at  contract  price  if  the  tests  are  satisfactory.     If 
the  tests  are  not  satisfactory  the  members  represented  by  them 
will  be  rejected. 

248.  Eye-Bar    Tests.     In  eye-bar  tests  the  fracture  shall  be 
silky,  the  elongation  in  10  ft.,  including  the  fracture,  shall  not 
be  less  than  15  per  cent;    and  the  ultimate  strength  and  true 
elastic  limit  shall  be  recorded.     (Par.  224.) 

PAINTING 

249.  Cleaning.     Steelwork,   before    leaving    the   shop,    shall 
be  thoroughly  cleaned  and  given  one  good  coating  of  pure  lin- 
seed oil,  or  such  other  paint  as  may  be  called  for  in  the  contract, 
well  worked  into  all  joints  and  open  spaces. 

250.  Contact  Surfaces.      In  riveted  work  the  surfaces  com- 
ing in  contact  shall  each  be  painted  before  being  riveted  together. 

251.  Inaccessible  Surfaces.     Pieces  and  parts  which  are  not 
accessible  for  painting  after  erection,  including  tops  of  stringers, 
eye-bar  heads,  ends  of  posts  and  chords,  etc.,  shall  have  a  good 
coat  of  paint  before  leaving  the  shop. 

252.  Condition    of   Surfaces.     Painting    shall    be    done  only 
when  the  "  surface  of  the  metal  is  perfectly  dry.     It  shall  not 
be  done  in  wet  or  freezing  weather,  unless  protected  under  cover. 

253.  Machine-Finished  Surfaces.       Machine-finished  surfaces 
shall  be  coated  with  white  lead  and  tallow  before  shipment  or 
before  being  put  out  into  the  open  air. 

254.  Painting    Omitted.      Rods,    wires,    hoops,    etc.,    used 
for  concrete  reinforcement  and  all  other  steelwork,  or  parts  of 
steelwork,  entirely  embedded  in  concrete  shall  not  be  painted. 


56  STANDARD  SPECIFICATIONS 

2,55.  Painting  after  Erection.  After  the  structure  is  erected 
the  metal  work  shall  be  cleaned  of  scale,  rust,  and  dirt,  and  then 
thoroughly  and  evenly  painted. 

Steelwork  in  buildings,  or  where  otherwise  protected  from 
exposure,  shall  have  one  additional  coat  of  paint,  mixed  with 
pure  linseed  oil,  or  as  specified  by  the  Engineer. 

Steelwork  in  bridges,  or  other  exposed  structures,  shall  have 
two  additional  coats  of  paint  as  specified. 

The  various  coats  of  paint  shall  be  of  distinctly  different 
shades  or  colors,  and  one  coat  must  be  allowed  to  dry  before 
the  next  is  applied. 

ERECTION 

256.  When  the  Contractor  Erects.     Whenever  the  contractor 
is  required  to  do  the  erection  this  requirement  shall  be  specific- 
ally stated  in  the   contract. 

The  erection  will  then  include  the  removal  of  any  existing 
structure,  all  necessary  hauling,  the  unloading  of  the  materials 
and  their  proper  care  until  the  completion  and  acceptance  of 
the  work,  as  specified  in  Pars.  257  to  263. 

257.  Removal  of  Old  Structure.     Whenever  new  structures 
are  to  replace  existing  ones  the  latter  shall  be  carefully  taken 
down,  marked  and  scheduled  to  facilitate  re-erection,  and  removed 
by  the  contractor  to  some  place  as  specified  in  the  contract. 

258.  Interruption  of  Traffic.     All  operations  shall  be  so  con- 
ducted as  not  to  impede  or  interrupt  the  work  of  other  con- 
tractors, the  traffic  of  any  railroad,  nor  close  any  thoroughfare 
or  waterway,  nor  conflict  with  any  law,  regulation,  or  ordinance 
of  any  properly  constituted   authority. 

259.  Permits.     Before   commencing   operations   the   contrac- 
tor shall,  at  his  own  expense,  obtain  all  necessary  permits  and 
comply  with  their  requirements. 

260.  Erection.      The   contractor   shall   furnish,   at    his   own 
expense,  all  necessary  staging,  falsework,  materials,  and  tools, 
and  shall  erect  the  structure  complete  and  paint  the  same.     (Pars. 
254,  255.) 

In  the  case  of  a  bridge,  or  trestle,  he  shall  furnish  and  frame 
all  floor  timbers,  guard  rails,  handrailings,  trestle  timbers,  etc., 
complete  ready  for  the  rails. 

Wherever   necessary    he    shall    drill   holes   in   the    masonry, 


INSPECTION,   PAINTING,  AND  ERECTION  57 

properly  place  all  anchor  bolts  and  securely  attach  them  to  the 
masonry  by  Portland  cement,  or  otherwise. 

261.  Safeguards  and  Damages.     The  contractor  shall  furnish, 
at  his  own  expense,  all  watchmen,  guards,  signals,  night  lights, 
etc.,  for  the  prevention  of  accidents,  and  be  responsible  for  the 
safety  of  the  structure;  and  he  shall  assume  full  responsibility 
for  all  accidents  to  men,  animals,  and  materials  before  the  com- 
pletion and  final  acceptance  of  the  structure  and  shall  indemnify 
the  purchaser  for  any  and  all  claims  for  damages  arising  there- 
from. 

262.  Defective    Work.     The    contractor    shall,    at    his    own 
expense,  remove,  rebuild,  or  make  good  any  damaged  material 
or  defective  work,  even  if  the   same  through  an  oversight   or 
otherwise  has  been  previously  accepted. 

263.  Clearing-up.     When  the  erection  is  completed  the  con- 
tractor shall,  at  his  own  expense,  remove  all  falsework,  rubbish, 
and  other  useless  material  caused  by  his  operations. 

264.  When   the   Purchaser   Erects.     In   case   the   purchaser 
erects  the  work  the  material  shall  be  delivered  on  cars  at  the 
railway  station  mentioned  in  the  contract. 

Any  extra  cost  incurred  by  the  purchaser,  during  the  erection, 
due  to  defective  material  or  workmanship,  shall  be  borne  by  the 
contractor. 


Of    THE 

UNIVERSITY 

Of 


PART  VII 

STRUCTURAL  TIMBER 

QUALITY 

265.  Kinds   of  Timber.     All  timber  for   structures   carrying 
live   loads  shall  preferably  be  of  longleaf  yellow  pine,   Douglas 
fir,  white  oak  or  western  hemlock;  for   other  structures  short- 
leaf  yellow   pine,  spruce,  white  pine  or   other  equivalent  good 
timber  may  be  used.     Chestnut  and  Norway  pine  may  be  used 
for  piles. 

266.  Quality    of    Timber.     All   timber   must    be    cut    within 
eighteen  (18)  months  of  the  time  of  delivery,  from  sound  trees 
and  sawed  to  standard  size.      (Par.  267.)     It  must  be  close  grained 
and  solid,  .free  from  defects  such  as  injurious  ring  shakes  and 
crooked   grain,   unsound   knots,   knots   in   groups,   decay,   large 
pitch  pockets,  or  other  defects  that  will  materially  impair  its 
strength  or  fitness  for  the  purpose  intended.     (Pars.  269  to  274.) 

267.  Size  of  Sawed  Timber.     All  timber  shall  be  sawed  true, 
out  of  wind  and  shall,  when  dry,  not  measure  scant  in  thickness 
more  than  the  following: 

^  in.,  for  flooring  and  boards  up  to  1J  in.  thick,  rough  size; 
i  in.,  for  planking  from  If  in.  to  5f  in.  thick,  rough  size; 
and 

|  in.,  for  dimension  timber  from  6  in.  thick  and  up,  rough  size. 

268.  Dressing  of  Sawed  Timber.     When  dressed  timber  over 
1J  in.  in  thickness  is  required  the  dimensions  specified  shall  refer 
to  rough  sizes,  unless  otherwise  mentioned. 

A   reduction  of  not  more  than  ^  in.,  beyond  that  specified 
in  Par.  267  will  be  allowed  for  each  planed  surface. 

269.  Shingles.     Shingles  shall  be  of  pine,  cedar,  or  cypress, 
as  specified  in  the  contract.     They  shall  be  from  16  to  IS  in.  in 
length,  from  4  to  6  in.  wide,  ^  in.  in  thickness  at  the  tip  and  from 

58 


STRUCTURAL  TIMBER  59 

^  to  ^  thick  at  the  butt.     They  shall,  in  the  first  10  in.  from  the 
butt,  be  absolutely  free  from  sap,  knots,  or  other  defects. 

270.  Piles.     Timber   piles   shall   preferably   be    of   Southern 
(longleaf  or  shortleaf)  yellow  pine,  white  oak,  Norway  pine  or 
cedar,  as  specified  in  the  contract. 

They  shall  be  cut  from  sound,  live  trees,  shall  be  straight 
and  free  from  wind-shakes,  large  knots,  decay,  and  other  impor- 
tant defects.  The  diameter  of  round  piles  near  the  butt  shall  not 
be  less  than  14  in.  or  more  than  16  in.,  and  at  the  tip,  of  piles 
under  40  ft.  in  length,  not  less  than  8  in.,  or  less  than  6  in.  in  any 
case. 

The}'  shall  taper  evenly  from  butt  to  tip  and  shall  be  so 
straight  that  a  straight  line,  drawn  from  center  to  center  of 
ends,  shall  at  no  point  fall  outside  of  the  circumference. 

All  piles  shall  be  cut  square  at  ends  and  they  shall  be  stripped 
of  their  bark.  (Par.  277.) 

271.  Flooring.     Flooring  shall  preferably  be  of  rift  shortleaf 
yellow  pine  or  maple  and  shall  be  furnished  in  two  grades  (prime 
and  common)  and  usually  in  lengths  between  4  and  16  ft.  and 
not  over  2^-in.  face.     The  thickness  of  flooring  shall  be  under- 
stood to  be  the  thickness  of  the  finished  material  after  dressing. 

The  exact  kind  of  wood,  grade,  width,  and  thickness  shall  be 
specified  in  the  contract. 

(a)  Prime  Flooring.     Prime  flooring  shall  be  edge  grained, 

kiln  dried,  matched,  tongued  and  grooved,  well  manu- 
factured so  as  to  be  free  from  planer's  marks,  edge 
splinters,  grain  slivers,  etc.  It  shall  show  one  face 
all  heart  and  shall  be  free  from  knots,  shakes,  sap,  and 
pitch  pockets. 

(b)  Common  Flooring.     Common  flooring  shall  be  like  prime 

flooring  except  that,  the  material  may  show  one  knot, 
not  over  1  in.  in  diameter,  to  every  4  ft.  in  length,  also 
unimportant  pitch  streaks  and  sap  stains. 

272.  Ceiling  and  Wainscoting.     Ceiling  and  wainscoting  shall 
be  graded  as  the  flooring,  but  shall  in  addition  be  double  beaded 
and  very  carefully  dressed. 

273.  Planks  and    Scantling.      Planks  and    scantling,  when 
used  for  floors,  struts,  cross  and  sway  bracing,  shall  show  one 
face  all  heart,  the  other  face  and  two  sides  shall  show  not  less 
than  75  per  cent  heart,  measured  across  the  face  or  sides  any- 


60 


STANDARD  SPECIFICATIONS 


where  in  the  piece.  It  shall  be  free  from  knots  H  in.  in  diameter 
and  over. 

When  used  for  other  purposes  it  shall  be  square  edged,  free 
from  knots  2\  in.  in  diameter  and  over,  and  wanes  not  extend- 
ing over  5  per  cent  of  the  surface  area  may  be  allowed  in  5  per 
cent  of  the  total  number  of  pieces  in  any  one  size. 

274.  Dimension  Timber.  Dimension  timber,  when  used  as 
beams,  bridge  joists,  or  stringers,  caps,  and  sills  in  trestles  and 
posts,  shall  show  not  less  than  75  per  cent  heart  on  each  of  the 
four  sides,  measured  across  each  side  anywhere  in  the  length 
of  the  piece.  No  loose  knots,  or  knots  greater  than  2%  in.  in 
diameter  or  over  one-quarter  (J)  the  width  of  the  face  of  the 
stick  in  which  they  occur,  will  be  allowed.  Knots  must  not  be  in 
groups,  or  be  located  within  3  in.  of  the  edges. 

When  used  for  other  purposes  it  shall  be  square  edged,  except 
it  may  have»l  in.  wane  on  one  corner  and  ring  shakes  must  not 
extend  over  one-eighth  (J)  of  the  length  of  the  piece. 


UNIT  STRESSES 

275.  Timber  in  Buildings  and  Highway  Bridges.  The 
maximum  stresses  due  to  the  combined  effect  of  dead,  snow, 
wind,  and  live  loads,  including  bending  and  impact,  if  any,  shall 
not  exceed  the  following  values  in  pounds  per  square  inch ; 


Timber. 

Bend- 
ing 
Ex- 
treme 
Fibers. 

Tension 

Compression. 

Shearing. 

With 
Grain. 

Across 
Grain. 

With 
Grain. 

Under 
15 
Diarn. 

900 

Across-  With 
Grain.  Grain. 

Across 
Grain. 

Douglas  fir  

1100 

1000 

1200 

300 

160 

800 

Hemlock,  western  

1000 

800 

1000 

750 

200 

150 

700 

Oak,  white  

1000 

1000 

200 

1300 

975 

450 

160 

1000 

Pine,  white  

800 

800 

50 

1000 

750 

150 

100 

600 

"      yellow,  Ion  gleaf. 
shortleaf  . 

1200 
1000 

1200 
900 

60 
50 

1300 
1100 

975 

825 

260 
180 

180 
170 

1200 
1000 

Spruce  

900 

800 

50 

1100 

825 

180 

100 

600 

For  columns  whose  length  does  not  exceed  lod  the  above 
values,  given  for  "  Compression  under  15  diameters/'  may  be 
used. 


STRUCTURAL  TIMBER 


61 


When  the  length  of  the  column  exceeds  lod  the  above  values, 
given  for  " Compression  with  grain/'  shall  be  reduced  as  follows: 


d 


=  c- 


where  S  =  allowable  working  stress  per  square  inch; 
c="  compression  with  grain  "  given  above; 
1  =  unsupported  lejigth  of  column  in  inches; 
d= least  width  of  column  in  inches; 

and  maximum  -7=45. 

276.  Timber  in  Railroad  Bridges  and  Trestles.  The  max- 
imum stresses  due  to  the  combined  effect  of  dead  and  live  loads, 
lateral  and  longitudinal  forces,  including  bending  and  impact, 
shall  not  exceed  the  following  values  in  pounds  per  square 
inch. 


Timber. 

Bend- 
ing Ex- 
treme 
Fibers. 

Tension. 

Compression.                 Shearing. 

! 

With        Across 
Grain.      Grain. 

With 
Grain. 

Under 
15 
Diam. 

Across   With 
Grain.  Grain. 

Across 
Grain. 

Douglas  fir  

1800 

1600 
1600 
1300 
2000 
1600 
1500 

1600      .... 

1300  :  

1600       325 
1300         80 
2000       100 
1500         80 
1300         80 

2000 
1600 
2100 
1600 
2100 
1800 
1800 

1400 
1120 
1470 
1120 
1470 
1260 
1260 

500  j  260 
320      250 
750      260 
250      160 
430      300 
300      280 
300      160 

1300 
1150 
1600 
1000 
2000 
1600 
1000 

Hemlock,  western  .  .  . 
Oak,  white  

Pine,  white  
'  '      yellow,  longleaf 
"       short  leaf 
Soruce.  . 

For  columns  whose  length  does  not  exceed  lod  the  above 
values,  given  for  "  Compression  under  15  diameters,"  may  be 
used. 

When  the  length  of  the  column  exceeds  lod  the  above  values, 
given  for  "  Compression  with  grain/'  shall  be  reduced  as  follows: 


- 

50d' 


62  STANDARD  SPECIFICATIONS 

where  S  =  allowable  working  stress  per  square  inch; 
d  =  "  compression  with  grain  "  given  above; 
I  =  unsupported  length  of  column  in  inches  ; 
d  =  least  width  of  column  in  inches; 

and  maximum  -r=35. 

277.  Piles.  The  maximum  load  per  pile  due  to  the  combined 
effect  of  dead  and  live  loads,  lateral  and  longitudinal  forces, 
including  impact,  if  any,  shall  not  exceed  the  following: 

2.5WH 

= 


where  P=  allowable  pressure  in  pounds  per  pile,  limited  as  per 

below  ; 

W=  weight  of  drop  hammer  in  pounds; 
H  =  height  of  drop  in  feet  ; 

s  =  average  sinking  in  inches  due  to  the  last  five  blows 
when  squarely  struck. 

When  the  piles  are  driven  through  wet  and  loose  soil  to  a  good 
bearing  the  pressure  shall  not  exceed  300  Ibs.  per  sq.in.  of  their 
average  cross-section.  When  driven  through  a  firm  soil  this 
pressure  may  be  increased  to  600  Ibs.  (Par.  270.) 

DETAILS  OF  DESIGN  F  '      '  \  '  *  •  • 

278.  Flooring    and    Joists     (Buildings).     Floor    planks    and 
floor  joists  in  buildings,  carrying  plastering,  shall  be  proportioned 
with  regard  to  their  stiffness,  limiting  their  deflection  to  one-three- 
hundred-and-sixtieth  Cj-J-g-)  of  the  span. 

All  other  timber  in  buildings  may  be  proportioned  with 
regard  to  its  strength. 

279.  Flooring    (Highway    Bridges).     Floor    planks    for    the 
roadway,  when  a  single  thickness  is  used  shall  have  a  minimum 
thickness  of  3  in.,  shall  be  laid  with  J-in.  open  spaces  and  shall 
be  securely  spiked  to  the  joists. 

Footwalk  planks  shall  have  a  minimum  thickness  of  2  in., 
shall  be  at  least  6  in.  wide  and  shall  be  spaced  with  J-in.  openings. 

Where  an  additional  wearing  surface  is  being  used,  the  min- 
imum thickness  of  which  shall  be  1J  in.,  the  thickness  of  the 


STRUCTURAL  TIMBER  63 

supporting  plank  may  be  reduced  to  2£  in.,  in  which  case  the 
latter  shall  be  laid  diagonally  with  ^-in.  openings. 

All  floor  planks  shall  be  laid  with  the  heart  side  down. 

280.  Joists     (Highway    Bridges).     The    minimum    size    of 
joists  shall  be  3"X12".     They  shall  be  notched  over  their  bear- 
ings at  least  ^  in.,  bringing  the  top  surfaces  to  exact  level.     Where 
they  rest  on  top  of  the  floor  beams  the  intermediate  joists  shall 
lap  by  each  other  over  the  full  width  of  same,  with  \  in.  open 
space  for  circulation  of  air,  whereas  the  outside  joists  shall  have 
their  outer  faces  flush  from  end  to  end  of  span. 

If  the  floor  plank  be  continuous  each  joist  may  be  assumed 
to  carry  only  two-thirds  (f)  of  the  concentrated  load. 

The  maximum  spacing  for  wooden  joists  shall  be  2  ft.  6  in. 

281.  Wheel  Guards    (Highway    Bridges).     There    shall   be  a 
wheel-guard  on  each  side  of  the  roadway  having  a  minimum 
size  of  4"X6",  laid  on  flat,  and   blocked   up  on   shims  2"X6" 
and  12  in.  long.     The  shims  shall  have  a  maximum  spacing  of  5 
ft .  from  center  to  center.     The  wheel  guards  shall  be  spliced  with 
half-and-half  joints  6  in.  long  over  a  shim  and  shall  be  fastened 
to  the  joist    beneath  with  a   three-quarter  (})  in.    bolt  passing 
through  the  center  of  each  shim. 

282.  Handrailing    (Highway   Bridges).     The   posts   shall   be 
6//X4//,  spaced  not  more  than  5  ft.  apart,  and  shall  be  firmly 
fastened.     There  shall  be  two   lines  of  railing  of  2"X6"  plank, 
the  upper  line  of  which  shall  be  placed  on  flat  and  the  lower 
one  on  edge. 

283.  Cross  Ties    (Railroad  Bridges).     The  cross  ties  shall  be 
of  such  size  as  to  give  the  requisite  resistance  to  bending,  under 
the  assumption   that  the   maximum  load  is  distributed  equally 
over  three  ties  and  that  the  impact  equals  100  per  cent. 

Every  tie  shall  be  notched  down  not  less  than  \  in.  and  be 
brought  to  a  full  and  even  bearing  upon  the  stringers,  and  every 
third  tie  shall  be  secured  thereto  by  a  f-in.  hook  bolt. 

The  minimum  sizes  of  cross  ties  shall  be: 

(a)  For  electric  railroads  6'' X 8'' X 8'  (laid  on  flat);   and, 

(6)   For  steam  railroads  8"X8"X10'. 

The  ties  shall  be  spaced  14  in.  center  to  center,  with  a  free  open- 
ing of  not  more  than  6  in.,  or  less  than  4  in. 

On  curves  the  super-elevation  of  the  outer  rail  shall  be  obtained 
by  using  beveled  ties. 


64  STANDARD  SPECIFICATIONS 

284.  Guard  Rails  (Railroad  Bridges).     The  minimum  size  of 
the  outer  guard  rails  shall  be  6"X8"  (laid  on  flat)  and  so  placed 
that  their  inner  faces  are  not  less  than  3  ft.  3  in.,  or  more  than 
3  ft.  6  in.,  from  center  of  track. 

The  minimum  size  of  the  inner  guard  rails  shall  be  6"XS" 
(laid  on  flat)  and  so  placed  that  their  outer  faces  are  not  less 
than  1  ft.  11  in.,  or  more  than  2  ft.  from  center  of  track. 

All  guard  rails  shall  be  continuous  over  piers  and  abutments; 
they  shall  be  spliced  with  half-and-half  joints  over  a  tie,  shall  be 
notched  1  in.  over  every  tie  and  shall  be  fastened  to  every  third 
tie  and  through  the  splice  by  a  three-quarter  (f)  in.  bolt.  The 
floor  system  shall  be  fastened  to  the  supporting  girders  by  a 
three-quarter  (f)  in.  hook  bolt  through  every  third  tie. 

All  heads  or  nuts  of  bolts  on  the  upper  faces  of  guard  rails 
shall  be  countersunk  into  the  wood  and  placed  in  a  cup  washer. 

285.  Pile  Trestles.     For  heights  less  than  30  ft.  pile  trestles 
may  be  used,  and  their  spacing,  center  to  center  of  bents,  shall 
not  exceed  15  ft.     Each  bent  whose  height  exceeds  10  ft.  shall 
be  braced  transversely  and,  if  it  exceeds  15  ft.,  shall  in  addition 
be  braced  longitudinally  in  at  least  every  fifth  panel. 

286.  Framed   Trestles.     For  trestles   of  greater  height  than 
30  ft.  framed  bents  shall  be  used.     They  shall  be  supported  upon 
foundations  of  concrete  piers,  timber  sills,  or  piles.     All  framed 
bents  shall  be  braced  transversely  and,  in  every  alternate  panel, 
longitudinally. 

287.  Trestle   Stringers.     Wherever  there   are   several   timber 
stringers   under   each   rail   they   shall   be   placed   symmetrically 
under  same.     The   stringers  shall  break  joints  over  the  bents, 
shall  be  securely  fastened  thereto,  and  shall  be  separated  from 
each  other  by  means  of  cast-iron  fillers  one-half   (^)   in.  thick 
spaced  not  over  5  ft.  apart. 


PART  VIII 

CEMENT 

The  following  specifications  for  cement  were  adopted  August 
15,  1908,  as  standard  by  the  American  Society  for  Testing 
Materials. 

GENERAL  OBSERVATIONS 

288.  (a)  These  remarks  (Pars.  288-293)  have  been  prepared 
with  a  view  of  pointing  out  the  pertinent  features  of  the  various 
requirements  and  the  precautions  to  be  observed  in  the  inter- 
pretation of  the  results  of  the  tests. 

(b)  The  committee  would  suggest  that  the  acceptance  or 
rejection  under  these  specifications  be  based  on  tests  made  by  an 
experienced  person  having  the  proper  means  for  making  the 
tests. 

289.  Specific  Gravity.     Specific  gravity  is  useful  in  detecting 
adulterations.     The  results  of  tests  of  specific  gravity  are  not 
necessarily  conclusive  as  an  indication  of  the  quality  of  a  cement, 
but  when  in  combination   with  the   results  of  other  tests  may 
afford  valuable  indications. 

290.  Fineness.     The  sieves  should  be  kept  thoroughly  dry. 

291.  Time  of   Setting.     Great   care   should   be   exercised   to 
maintain  the  test  pieces  under  as  uniform  conditions  as  possible. 
A  sudden  change  or  wide  range  of  temperature  in  the  room  in 
which  the  tests  are  made,  a  very  dry  or  humid  atmosphere,  and 
other  irregularities,  vitally  affect  the  rate  of  setting. 

292.  Tensile  Strength.     Each  consumer  must  fix  the  minimum 
requirements  for  tensile  strength  to  suit  his  own  conditions.     They 
shall,  however,  be  within  the  limits  stated. 

293.  Constancy  of  Volume : 

(a)  The  tests  for  constancy  of  volume  are  divided  into  twro 
classes,  the  first  normal,  the  second  accelerated.  The 
latter  should  be  regarded  as  a  precautionary  test  only, 
and  not  infallable.  So  many  conditions  enter  into  the 

65 


66  STANDARD  SPECIFICATIONS 

making  and  interpreting  of  it  that  it  should  be  used 
with  extreme  care. 

(b)  In  making  the  pats  the  greatest  care  should  be  exercised 

to  avoid  initial  strains  due  to  molding  or  to  too  rapid 
drying-out  during  the  first  twenty-four  hours.  The 
pats  should  be  preserved  under  the  most  uniform 
conditions  possible,  and  rapid  changes  of  temperature 
should  be  avoided. 

(c)  The  failure  to  meet  the  requirements  of  the  accelerated 

tests  need  not  be  sufficient  cause  for  rejection.  The 
cement  may,  however,  be  held  for  twenty-eight  days, 
and  a  retest  made  at  the  end  of  that  period,  using  a  new 
sample.  Failure  to  meet  the  requirements  at  this  time 
should  be  considered  sufficient  cause  for  rejection, 
although  in  the  present  state  of  our  knowledge  it  can- 
not be  said  that  such  failure  necessarily  indicates  un- 
soundness,  nor  can  the  cement  be  considered  entirely 
satisfactory  simply  because  it  passes  the  tests. 

SPECIFICATIONS 
294.  General  Conditions: 

(a)  All  cement  shall  be  inspected. 

(b)  Cement  may  be  inspected  either  at  the  place  of  manu- 

facture  or   on  the  work. 

(c)  In  order  to  allow  ample  time  for  inspection  and  testing, 

the  cement  should  be  stored  in  a  suitable  weather-tight 
building  having  the  floor  properly  blocked  or  raised 
from  the  ground. 

(d)  The  cement  shall  be  stored  in  such  a  manner  at  to  permit 

easy  access  for  proper  inspection  and  identification  of 
each  shipment. 

(e)  Every  facility  shall  be  provided    by  the   contractor  and 

a  period  of  at  least  twelve  days  allowed  for  the  inspec- 
tion and  necessary  tests. 

(/)  Cement  shall  be  delivered  in  suitable  packages  with  the 
brand  and  name  of  manufacturer  plainly  marked  thereon. 

(g)  A  bag  of  cement  shall  contain  94  Ibs.  of  cement  net. 

Each  barrel  of  Portland  cement  shall  contain  4  bags, 
and  each  barrel  of  natural  cement  shall  contain  3  bags 
of  the  above  net  weight. 


CEMENT  67 

(h)  Cement  failing  to  meet  the  7-day  requirements  may  be 
held  awaiting  the  results  of  the  28-day  tests  before 
rejection. 

(i)  All  tests  shall  be  made  in  accordance  with  the  methods 
proposed  by  the  Committee  on  Uniform  Tests  of  Cement 
of  the  American  Society  of  Civil  Engineers,  presented 
to  the  Society,  January  21,  1903,  and  amended  January 
20,  1904,  and  January  15,  1908,  with  all  subsequent 
amendments  thereto. 

(j)  The  acceptance  or  rejection  shall  be  based  on  the  following 
requirements:.  (Pars.  295  to  306.) 

NATURAL  CEMENT 

295.  Definition.     This  term   shall   be   applied   to   the   finely 
pulverized  product  resulting  from  the  calcination  of  an  argil- 
laceous limestone  at  a  temperature  only  sufficient  to  drive  off  the 
carbonic  acid  gas. 

296.  Fineness.     It   shall  leave  by  weight  a  residue   of  not 
more  than  10  per  cent  on  the  No.  100,  and  30  per  cent  on  the  No. 
200  sieve. 

297.  Time  of  Setting.     It  shall  not  develop  initial  set  in  less 
than  10  minutes,  and    shall  not  develop    hard  set  in  less  than 
30  minutes,  or  in  more  than  3  hours. 

298.  Tensile  Strength.     The  minimum  requirements  for  ten- 
sile strength  for  briquettes  1  in.  square  in  cross-section  shall  be 
within  the  following  limits,  and  shall  show  no   retrogression  in 
strength  within  the  periods  specified:* 

NEAT  CEMENT 
Age.  Strength. 

24  hours  in  moist  air 50-100  Ibs. 

7  days  (1  day  in  moist  air,    6  days  in  water)  100-200  " 

28  days  (1  27        "       "       ) 200-300  " 

ONE   PART  CEMENT,   THREE   PARTS  STANDARD   SAND 

7  days  (1  day  in  moist  air,    6  days  in  water) 25—75    Ibs. 

28  days  (1  27      "  ) 75-150  " 

*  For  example,  the  minimum  requirement  for  the  24-hour  neat  cement 
test  should  be  some  specified  value  within  the  limits  of  50  and  100  Ibs.,  and  so 
on  for  each  period  stated. 


68  STANDARD  SPECIFICATIONS 

If  the  minimum  strength  is  not  specified,  the  mean  of  the  above 
values  shall  be  taken  as  the  minimum  strength  required. 

299.  Constancy  of  Volume.     Pats  of  neat  cement  about  3-in. 
in  diameter,  i-in.  thick  at  center,  tapering  to  a  thin  edge,  shall 
be  kept  in  moist  air  for  a  period  of  24  hours. 

(a)  A  pat  is  then  kept  in  air  at  normal  temperature. 

(6)  Another  is  kept  in   water  maintained  as  near  70°,  F.   as 

practicable. 
(c)  These  pats  are  observed  at  intervals  for  a  least  28  days, 

and,  to  satisfactorily  pass  these  tests,   should  remain 

firm  and  hard  and  show  no  signs  of  distortion,  checking, 

cracking,  or  disintegrating. 

PORTLAND  CEMENT 

300.  Definition.     This  term  applies  to  the  finely  pulverized 
product  resulting  from  the  calcination  to  incipient  fusion  of  an 
intimate  mixture  of  properly  proportioned  argillaceous  and  cal- 
careous materials,  and  to  which  no  addition  greater  than  3  per 
cent,  has  been  made  subsequent  to  calcination. 

301.  Specific  Gravity.      The  specific  gravity  of  the   cement t 
ignited  to  a  low  red  heat,  shall  be  not  less  than  3.10,  and  the 
cement  shall  not  show  a  loss  on  ignition  of  more  than  4  per  cent. 

302.  Fineness.     It   shall  leave  by  weight   a   residue   of  not 
more  than  8  per  cent  on  the  No.  100,  and  not  more  than  25  per 
cent  on  the  No.  200  sieve. 

303.  Time  of  Setting.     It  shall  not  develop  initial  set  in  less 
than  30  minutes,  and  must  develop  hard  set  in  not  less  than  1 
hour,  nor  more  than  10  hours. 

304.  Tensile    Strength.      The     minimum     requirements     for 
tensile  strength  for  briquettes  1  in.  square  in  section  shall  be 
within  the  periods  specified.* 

NEAT  CEMENT 
Age.  Strength. 

24  hours  in  moist  air 150-200  Ibs. 

7  days  (1  day  in  moist  air,    6  days  in  water) 450-550  " 

28  days  (1  27       "  ) 550-650  " 

*  For  example,  the  minimum  requirement  for  the  24-hour  neat  cement 
test  should  be  some  specified  value  within  the  limits  of  150  and  200  Ibs., 
and  so  on  for  each  period  stated. 


CEMENT  69 

ONE  PART  CEMENT,   THREE   PARTS  STANDARD  SAND 

7  days  (1  day  in  moist  air,    6  days  in  water) 150-200  Ibs. 

28  days  (1  27  ) 200-300  " 

If  the  minimum  strength  is  not  specified,  the  mean  of  the  above 
values  shall  be  taken  as  the  minimum  strength  required. 

305.  Constancy   of    Volume.     Pats    of    neat    cement    about 
3  in.  in  diameter,  ^  in.  thick  at  center,  and  tapering  to  a  thin 
edge,  shall  be  kept  in  moist  air  for  a  period  of  24  hours. 

(a)  A  pat  is  then  kept  in  air  at  normal  temperature  and 
observed  at  intervals  for  at  least  28  days. 

(6)  Another  pat  is  kept  in  water  maintained  as  near  70°  F. 
as  practicable,  and  observed  at  intervals  for  at  least 
28  days. 

(c)  A  third  pat  is  exposed  in   any   convenient   wray  in   an 

atmosphere  of  steam,  above  boiling  water,  in  a  loosely 
closed  vessel  for  5  hours. 

(d)  These  pats,  to  satisfactorily  pass  the  requirements,  shall 

remain  firm  and  hard  and  show  no  signs  of  distortion f 
checking,  cracking,  or  disintegrating. 

306.  Sulphuric  Acid  and  Magnesia.     The   cement  shall  not 
contain  more  than  1.75  per  cent  of  anhydrous  sulphuric 
acid  (SO3) ,  nor  more  than  4  per  cent  of  magnesia  (MgO) . 


PART   IX 

PORTLAND-CEMENT  CONCRETE 

THE  following  specifications  for  Portland-cement  concrete 
were  adopted  in  1904,  as  standard  by  the  American  Railway 
Engineering  and  Maintenance  of  Way  Association,  see  Pro- 
ceedings, Vol.  V. 

307.  Cement.     The  cement  shall  be  Portland,  either  American 
or  foreign,  which  will  meet  the  requirements  of  the  standard 
specifications    adopted    by   the    American    Society    for    Testing 
Materials.     (See  Part  VIII.) 

308.  Sand.      The  sand    shall  be  clean,  sharp,  coarse,  and  of 
grains  varying  in  size.     It  shall  be  free    from  sticks  and  other 
foreign  matter,  but  it  may  contain  clay  or  loam  not  to  exceed 
5  per  cent.     Crusher  dust,  screened  to  reject  all  particles  over 
-i  in.  in  diameter,  may  be  used  instead  of  sand,   if  approved  by 
the  Engineer. 

309.  Stone.     The   stone  shall  be   sound,   hard,   and   durable, 
crushed  to  sizes  not  exceeding  2  in.  in  any  direction.     For  rein- 
forced concrete,  the  sizes  usually  are  not  to  exceed  J  in.  in  any 
direction,  but  may  be  varied  to  suit  the  character  of  the  rein- 
forcing material. 

310.  Gravel.     The  gravel  shall  be  composed  of  clean  pebbles 
of  hard  and  durable  stones  of  sizes  not  exceeding  2  in.  in  diam- 
eter, free  from  clay  and  other  impurities  except   sand.     When 
containing    sand    in    any    considerable    quantity,    the    amount 
per  unit  of  volume  of  gravel  shall  be  determined  accurately  to 
admit  of  the  proper  proportion  of  sand  being  maintained  in  the 
concrete  mixture. 

311.  Water.      The    water    shall    be    clean    and    reasonably 
clear,  free  from  sulphuric  acid  and  strong  alkalies. 

312.  Mixing  by  Hand : 

(a)  Tight  platforms  shall  be  provided   of  sufficient   size  to 
accommodate   men   and   materials   for  the   progressive 

70 


PORTLAND-CEMENT  CONCRETE  71 

and  rapid  mixing  of  at  least  two  batches  of  concrete 
at  the  same  time.  Batches  shall  not  exceed  1  cubic 
yard  each,  and  smaller  batches  are  preferable,  based 
upon  a  multiple  of  the  number  of  sacks  to  the  barrel. 

(b)  Spread   the   sand   evenly   upon  the   platform,   then   the 

cement  upon  the  sand,  and  mix  thoroughly  until  of 
an  even  color.  Add  all  the  water  necessary  to  make 
a  thin  mortar,  and  spread  again;  add  the  gravel  if  used, 
and  finally  the  broken  stone,  both  of  which,  if  dry, 
should  first  be  thoroughly  wet  down.  Turn  the  mass 
with  shovels  or  hoes  until  thoroughly  incorporated, 
and  until  all  the  gravel  and  stone  is  covered  with  mor- 
tar, which  will  probably  require  the  mass  to  be  turned 
four  times. 

(c)  Another  method,  which  may  be  permitted  at  the  option 

of  the  engineer  in  charge,  is  to  spread  the  sand,  then 
the  cement,  and  mix  dry;  then  the  gravel  or  broken 
stone,  add  water,  and  mix  thoroughly  as  above. 

313.  Mixing  by  Machine.     A  machine  mixer  shall  be  used 
wherever  the  volume  of  work  will  justify  the  expense  of  installing 
the  plant.     The  necessary  requirements  for  the  machine  shall 
be  that  a  precise  and  regular  proportioning  of  materials  can  be 
controlled,  and  the  product  as  delivered  shall  be  of  the  required 
consistency  and  be  thoroughly  mixed. 

314.  Consistency.     The  concrete  shall  be  of  such  consistency 
that  when  dumped  in  place  it  will  not  require  much  tamping. 
It  shall  be  spaded  down,  and  be  tamped  sufficiently  to  level  it 
off,  after  which  the  water  should  rise  freely  to  the  surface. 

315.  Forms: 

(a)  Forms  shall  be  well  built,  substantial  and  unyielding, 
properly  braced  or  tied  together  by  means  of  wire  or 
rods,  -and  shall  conform  to  the  lines  given. 

(6)  For  all  important  work,  the  lumber  used  for  face  work 
shall  be  dresse^d  on  one  side  and  both  edges,  and  shall 
be  sound  and  free  from  loose  knots,  secured  to  the 
studding  or  uprights  in  horizontal  lines. 

(c)  For  backing  and   other  rough   work,   undressed  lumber 

may  be  used. 

(d)  Where    corners   of   the   masonry   and   other   projections 

liable    to    injury    occur,    suitable    moldings    shall    be 


72  STANDARD  SPECIFICATIONS 

placed  in  the  angles  of  the  forms  to  round  of  bevel 
them  off. 

(e)  Lumber  once  used  in  forms  shall  be  cleaned  before  being 
used  again. 

(/)  The  forms  must  not  be  removed  within  36  hours 
after  all  the  concrete  in  that  section  has  been  placed. 
In  freezing  weather,  they  must  remain  until  the  con- 
crete has  had  sufficient  time  to  become  thoroughly 
hardened. 

(g)  In  dry  but  not  freezing  weather,  the  forms  shall  be  drenched 
with  water  before  the  concrete  is  placed  against  them. 

316.  Depositing: 

(a)  Each  layer  should  be  left  somewhat  rough  to  insure  bond- 
ing with  the  next  layer  above;  and,  if  the  concrete 
has  already  set,  it  shall  be  thoroughly  cleaned  by  scrub- 
bing with  coarse  brushes  and  water  before  the  next 
layer  is  placed  upon  it. 

(6)  Concrete  shall  be  deposited  in  the  molds  in  layers  of  such 
thickness  and  position  as  shall  be  specified  by  the 
Engineer  in  charge.  Temporary  planking  shall  be 
placed  at  the  ends  of  partial  layers,  so  that  none  shall 
run  out  to  a  thin  edge.  In  general,  excepting  in  arch 
work,  all  concrete  must  be  deposited  in  horizontal 
layers  of  uniform  thickness  throughout. 

(c)  The  work  shall  be  carried  up  in  sections  of  convenient 

length  and  the  sections  shall  be  completed  without 
intermission. 

(d)  In  no  case  shall  work  on  a  section  stop  within  18  in.  of 

the  top. 

(e)  Concrete  shall  be  placed  immediately  after  mixing,  and 

any  having  an  initial  set  shall  be  rejected. 

317.  Expansion  Joints: 

(a)  In  exposed  work,  expansion  joints  may  be  provided  at 
intervals  of  30  to  100  ft.,  as  the  character  of  the  struc- 
ture may  require. 

(6)  A  temporary  vertical  form  or  partition  of  plank  shall  be 
set  up,  and  the  section  behind  shall  be  completed  as 
though  it  were  the  end  of  the  structure.  The  partition 
shall  be  removed  when  the  next  section  is  begun,  and 
the  new  concrete  shall  be  placed  against  the  old  without 


PORTLAND-CEMENT  CONCRETE 


73 


mortar  flushing.     Locks  shall  be  provided,  if  directed 
or  called  for  by  the  plans. 

(c)  In  reinforced  concrete  the  length  of  these  sections  may  be 
materially  increased  at  the  option  of  the  Engineer. 

318.  Facing: 

(a)  The  facing  may  be  made  by  carefully  working  the  coarse 
stone  back  from  the  form  by  means  of  a  shovel,  bar,  or 
similar  tool,  so  as  to  bring  the  excess  mortar  of  the  con- 
crete to  the  face. 
Or, 

(6)  About  1  in.  of  mortar  (not  grout)  of  the  same  pro- 
portion as  used  m  the  concrete  may  be  placed  next  to 
the  forms  immediately  in  advance  of  the  concrete,  in 
order  to  secure  a  perfect  face. 

(c)  Care  must  be  taken  to  remove  from  the  inside  of  the 
forms  any  dry  mortar  in  order  to  secure  a  perfect  face. 

319.  Proportions.     The  proportions  of  the  materials  in  the 
concrete  shall  be  as  specifically  called  for  by  contract,  or  as  set 
forth  herein,  upon  the  lines  left  for  that  purpose,  the  volume  of 
cement  to  be  based  upon  the  actual  cubic  contents  of  1  barrel 
of  specified  weight. 


Structure. 


Parts  by  Volume 


Gravel.      Broken  Stone. 


320.  Finishing: 

(a)  After  the  forms  are  removed,  which  should  generally  be 
as  soon  as  possible  after  the  concrete  is  sufficiently 
hardened,  any  small  cavities  or  openings  in  the  face 
shall  be  neatly  filled  with  mortar,  if  necessary  in  the 
opinion  of  the  Engineer.  Any  ridges  due  to  cracks 
or  joints  in  the  lumber  shall  be  rubbed  down  with  chisel 
or  wooden  float.  The  entire  face  may  then  be  washed 
with  a  thin  grouts  of  the  consistency  of  whitewash, 


74  STANDARD  SPECIFICATIONS 

mixed  in  the  same  proportion  as  the  mortar  of  the 
concrete.  The  wash  shall  be  applied  with  a  brush. 
The  earlier  the  above  operations  are  performed  the 
better  will  be  the  result. 

(6)  The  tops  of  bridge  seats,  pedestals,  copings,  wing  walls, 
etc.,  when  not  finished  with  natural  stone  coping,  shall 
be  finished  with  a  smooth  surface  composed  of  one  part 
cement  to  two  parts  of  granite  or  other  suitable  screen- 
ings or  sand,  applied  in  a  layer  J  to  1  in.  thick.  This 
must  be  put  in  place  with  the  last  course  of  concrete. 

321.  Waterproofing.     Where    waterproofing    is    required,    a 
thin  coat  of  mortar  or  grout  shall  be  applied  for  a  finishing  coat, 
upon  which  shall  be  placed  a  covering  of  suitable  waterproofing 
material. 

322.  Freezing  Weather.     Ordinarily  concrete  to  be  left  above 
the  surface  of  the  ground  shall  not  be  constructed  in  freezing- 
weather.     Portland-cement  concrete  may  be  built  under  these 
conditions  by  special  instructions.     In  this  case  the  sand,  water, 
and  broken  stone  shall  be  heated;  and  in  severe  cold,  salt  shall 
be  added  in  the  proportion  of  about  2  Ibs.  per  cubic  yard. 

323.  Reinforced  Concrete.     (See  Part  X.) 


PART  X 

REINFORCED  CONCRETE 

GENERAL  REQUIREMENTS 

324.  Preparation  of  Plans.     All  plans  shall  be  prepared,  and 
drawn  to  a  scale  sufficiently  large  so  as  to  show  clearly  the  quan- 
tity and  the  exact  position  of  all  reinforcement;  the  method  of  its 
anchorage,  where  continuity  or  extra  bonding  are  required;  and 
in  short  all  details  of  parts  affecting  strength  or  appearance. 

325.  Adherence    to    Plans.      The    contractor    shall,    during 
construction,  adhere  strictly  to  the  plans,  as  the  strength  of  the 
finished   structure   depends  upon  this;  and  the  inspector   shall 
not  be  allowed  to  make  any  changes  therein  without  the  written 
authority  of  the  engineer. 

326.  Placing   of  Forms: 

(a)  The  falsework  and  forms  shall  be  substantial  and  unyield- 
ing, properly  braced  or  tied  together  by  means  of  wire 
or  rods,  and  shall  be  so  designed  that  the  concrete  will 
conform  to  the  proper  dimensions  and  contours. 

(6)  The  timber  used  shall  not  be  too  dry,  as  a  free  absorption 
of  moisture  will  cause  swelling  and  consequent  deform- 
ation of  the  concrete;  it  shall  be  planed  smooth  on 
both  edges  and  one  side,  shall  be  covered  with  a  coating 
of  oil,  soap,  limewash  or  other  substance  to  prevent  the 
concrete  from  adhering  to  the  surface,  and  shall  have 
all  joints  closed  so  as  to  prevent  the  leakage  of  grout. 

(c)  In  general  the  forms  shall  be  simple  of  construction,  easy 

of  erection,  maintenance,  and  removal,  and  they  shall 
frequently  be  inspected  during  the  progress  of  the  work 
that  perfect  alignment  may  be  maintained. 

(d)  All  forms  having  been  previously  used  shall  be  thoroughly 

cleansed  and  prepared  before  being  used  again. 

327.  Metal    Reinforcement.     Xo    metal    reinforcement    used 
in  concrete  shall  be  painted,  but  shall  be  free  from  dirt,  oil,  or 

75 


76  STANDARD  SPECIFICATIONS 

grease.  All  mil]  scale  shall  be  removed  by  hammering  the  metal, 
or  preferably  by  pickling  the  same  in  a  weak  solution  of  muriatic 
acid. 

328.  Placing   of    Reinforcement.     The    metal    reinforcement 
shall  be  placed  and  kept  during  the  deposition  and  tamping  of 
the  concrete  in  the  proper  position.     Whenever  it  is  practicable 
it  shall  be  placed  in  position  first.     This  can  usually  be  done 
where  the  metal  occurs  in  the  bottom  of  the  forms,  by  supporting 
it  on  transverse  wires  or  otherwise. 

329.  Ingredients.     The     contract     covering     any     reinforced 
concrete  work  shall  specifically  state  the  quality  of  the  cement 
and  the   aggregates   and,   if  possible,   the  particular  brands   of 
cement,  sand,  gravel,  or  broken  stone  to  be  used;  shall  state  the 
exact  proportions  of  cement  and  aggregates  and  the  approxi- 
mate proportion  of  water  to  be  mixed,  and  the  required  strength 
in  compression  to  be  attained  in  28  days  by  test  cylinders  8 
in.  in  diameter  and  16  in.  long. 

Methods  of  measurements  of  the  proportions  of  the  various 
ingredients,  including  the  water,  shall  be  used,  which  will  secure 
separate  uniform  measurements  at  all  times,  preferably  by 
weight. 

330.  Mixing  by  Hand.     (See  Par.  312.) 

331.  Mixing  by  Machine.     (See  Par.  313.) 

332.  Consistency.     The     materials     should     be     mixed     wet 
enough  to  produce  a  concrete  of  such  a  consistency  as  will  flow 
into  the  forms  and  about  the  metal  reinforcement,  and,  at  the 
same  time,  can  be  conveyed  from  the  mixer  to  the  forms  without 
separation   of  the  coarse  aggregates  from  the  mortar. 

333.  Placing  of  Concrete: 

(a)  Before  placing  the  concrete  care  shall  be  taken  to  see 
that  the  forms  are  thoroughly  wetted  and  the  space 
to  be  occupied  by  the  concrete  is  free  from  debris. 

(6)  Great  care  must  also  be  taken  to  insure  the  coating  of 
the  metal  with  cement  mortar  and  the  thorough  flushing 
of  the  bottoms  of  the  forms  with  same;  after  which  the 
concrete  must  be  deposited  rapidly,  thoroughly  com- 
pacting it  around  the  metal. 

(c)  Concrete,  after  the  addition  of  water  to  the  mix,  shall 
be  handled  rapidly,  in  as  small  masses  as  is  practicable, 
from  the  place  of  mixing  to  the  place  of  final  deposit. 


REINFORCED  CONCRETE  77 

(d)  No  concrete  having  an  initial  set  shall  be  used,  nor  shall 

the  retempering  of  mortar  or  concrete  (i.e.,  remixing 
with  water  after  it  has  partially  set)  be  permitted. 

(e)  Where  the  metal  reinforcement  occurs  in  several  layers 

the  concrete  shall  be  deposited  in  equal  layers  and 
rammed  separately.  Otherwise  the  concrete  shall  be 
spread  in  horizontal  layers  not  exceeding  4  in.  in 
slabs,  or  6  in.  in  any  case. 

(/)  The  concrete  shall  be  deposited  in  a  manner  that  will 
permit  the  most  thorough  compacting,  such  as  can 
be  obtained  by  working  with  a  straight  shovel  or  slic- 
ing tool  kept  moving  up  and  down  till  all  the  ingredients 
have  settled  in  their  proper  place  by  gravity  and  the 
surplus  water  is  forced  to  the  surface. 

(g)  In  columns  having  circumferential  reinforcement  the 
concrete  shall  preferably  be  introduced  by  means  of  a 
tremie  or  tube,  in  order  to  prevent  the  ingredients 
from  sorting  in  layers.  To  prevent  settlement  or 
shrinkage  in  freshly  made  columns  a  period  of  at  least 
two  hours  shall  elapse  before  any  girder  or  beam  over 
them  may  be  commenced. 

(h)  In  depositing  concrete  under  water  special  care  shall 
be  exercised  to  prevent  the  cement  from  floating  away 
and  to  prevent  the  formation  of  lait  ance ;  when  lait  ance 
has  formed  it  shall  be  removed  before  placing  fresh 
concrete. 

(i)  When  work  is  resumed  concrete  previously  placed  shall 
be  roughened,  thoroughly  cleansed  of  foreign  material 
and  laitance,  drenched  and  slushed  with  a  mortar 
consisting  of  1  part  Portland  cement  and  2  parts 
sand. 

(/)  The  faces  of  concrete  exposed  to  premature  drying  should 
be  kept  wet  for  a  period  of  at  least  7  days  after 
molding. 

334.  Freezing  Weather.  Concrete  for  reinforced  structures 
shall  not  be  mixed  or  deposited  at  a  freezing  temperature,  except 
under  special  instruction.  In  this  case  the  sand,  water,  and 
broken  stone  shall  be  heated,  but  no  salt  shall  be  added. 

Effective  means  shall  be  provided  to  prevent  the  concrete 
from  freezing  until  it  has  thoroughly  hardened. 


78  STANDARD  SPECIFICATIONS 

335.  Removal  of  Forms: 

(a)  The   t;me   for  removal   of  forms   and   shores,    being   an 

extremely  important  consideration,  shall  be  determined 
in  each  case  by  the  engineer  after  inspection.  As  a 
guide  the  following  important  determinants  are  men- 
tioned; size  of  structure  and  general  dimensions  of  parts; 
methods  of  mixing  and  proportions  of  mixture;  whether 
slow  or  quick-setting  cements  are  used;  atmospheric 
conditions;  importance  of.  live  loading  and  its  ratio 
to  the  dead  load;  length  of  period  between  the  removal 
of  forms  and  shores  and  the  time  when  the  maximum 
loading  may  be  attained,  etc.  But  in  any  case  the 
supporting  shores  shall  be  left  in  place  until  their  re- 
moval is  permitted  by  the  engineer. 

(b)  The  minimum  time  for  the  removal  -of  Forms   (not  the 

supporting  shores  shall  be  as  follows: 
For  Bottom  of  Slabs  4  days,  for  spans  of  4  ft.  or  less,  plus 

1  day  extra  for  each  additional  foot  of  span. 
For  Sides  and  Beams  and  Girders  7  days. 
For  Columns  4  days. 
For  Bridge  Arches  28  days. 

(c)  The  minimum  time  for  the  removal  of  Shores  shall  be  as 

follows : 
For  Bottoms  of  Beams  and  Girders  21  days,  for  spans  of 

10  ft.  or  less,  plus  one-half  (^)  day  for  each  additional 

foot  of  span. 
The  original  shores  must  in  no  case  be  taken  down,  replaced 

or  disturbed,  until  permitted  by  the  Engineer. 

(d)  When  frosty  weather  occurs  during  the  above  periods  an 

extension  of  time  shall  be  made  equal  to  its  duration. 

(e)  During  the  setting  and  before  the  removal  of  forms  no 

extraneous  loading  shall  be  placed  upon  the   concrete. 
(/)  The  forms  shall  be  removed  with  care  so  as  not  to  deface 
the  structure  or  to  disturb  the  remaining  supports. 

LOADS 

336.  Dead  Load.     The  dead  load  consists  of: 

(a)  The   weight   of  the  reinforced   concrete,   which   shall   be 
taken  at  150  Ibs.  per  cubic  foot. 


REINFORCED  CONCRETE  79 

(6)  The  weight  of  the  roof  covering,  flooring,  paving,  or  ballast, 
if  any.     (For  weight  of  same  see  Pars.  3,  4,  5,  59,  109.) 

(c)  The   weight   of  railway   tracks,  if  any.      (For  weights  of 

same  see  Pars.  59,  109.) 

(d)  The  snow  load,  if  any.     (For  weight  of  same  see  Par.  6.) 

337.  Wind  Pressure  or  Lateral  Forces.     (See  Pars.  7,  62,  113, 
114.) 

338.  Centrifugal  Forces.     (See  pars.  63,  116.) 

339.  Traction  Forces.     (See  Pars.  64,  115.) 

340.  Live  Loads.     (See  Pars.  9,  10,  60,  110,  111.) 

341.  Impact.     An  impact  allowance   shall   be   added  to  the 
computed  maximum  live-load  stresses,  as  follows: 

(a)    For     floors     of      schools,     theaters,  1  /    inn    \ 

churches,     armories,     dancing     or  \  Impact  =  S  f  ,     oAn)» 
other  public  halls  and  factories  .  .  .  .  J 

(6)   For  floors  carrying  moving  machinery  j  ,  . 

for  crane  girders   and   posts;     for  [•  Impact  =  S  (-=—  -      ^j. 

r  .    i  i_    •  j  V-1  T  oUU/ 

highway  bridges  .................  J 

300    \ 


( 
T 
/> 


OAn. 

T-  oUU 


where  S=  computed  maximum  live-load  stress,  moment  or  shear, 
L  =  length  of  span  in  feet,  or  loaded  length  of  span,  which- 
ever gives  a  maximum. 

No  impact  allowance  shaj^be  added  to  stresses  produced  by 
traction,  centrifugal,  and  lateral  or  wind  forces. 

CALCULATION  OF  STRESSES 

342.  General  Dimensions.     The    following    dimensions    shall 
first  be  calculated  or  assumed: 

Span  of  slabs,  supported  at  ends,  clear  opening  plus  thick- 
ness of  slab. 

Span  of  slabs,  continuous,  c.  to  c.  of  beams. 

Span  of  beams  and  girders,  c.  to  c.  of  support. 

Length   of   columns,  the  maximum  unsupported  length. 

343.  Assumptions: 

(a)  The  ratio  of  the  modulus  of  elasticity  of  steel  (E8)  [to 
the  modulus  of  elasticity  of  concrete  (Ee)  shall  be  taken 
at  15,  or  E.  +  Ee  =  15. 


80 


STANDARD  SPECIFICATIONS 


(6)  The  modulus  of  elasticity  of  concrete  in  compression 
is  constant,  and  the  relation  of  stress  to  strain  in  con- 
crete is  rectilinear. 

(c)  In  calculating  the  moment  of  resistance  of  slabs,  beams, 
or  girders  the  tensile  value  of  the  concrete  shall  be 
neglected. 

344.  Bending  Moments.  The  bending  moments  shall  be 
computed  as  follows: 

(a)   For  slabs,  reinforced  in  one  direction  only, 

When  supported  at  both  ends,M=  1.5wL2,  at  center 

=  0  at  ends 

When  supported  at  one  end,  1  , ..  ,  9 

.  *  \M=1.2wL2,  at  center 

continuous  at  other  j 

0  at  one  end 
-  1.2wL2  Sit  the  other. 
When  continuous,  or  fixed  ~\M  =  wL2,  at  center, 
at  both  ends,  —  wL2  at  ends, 

where  M= bending  moment  in  inch-pounds; 

w  =  dead  or  live  load  in  pounds  per  linear  foot,  uniformly 

distributed ; 
L  =  length  of  span  in  feet.     (Par.  342.) 

(6)  For  slabs  whose  length  does  not  exceed  1J  times  their 
width  and  which  are  reinforced  in  both  directions, 
the  loading  shall  be  assumed  to  be  divided  between  the 
transverse  and  the  longitudinal  systems,  as  follows: 


Ratio  of  long  to  short  side  

1 

1.1 

1.15 

1.2 

1.25 

Proportion  of  loading  carried  by  trans- 
|  verse  svstem. 

0  50 

0  59 

0  64 

0  67 

0.71 

Do.  by  longitudinal  system  .       

0.50 

0.41 

0.36 

0.33 

0.29* 

and  shall  be  distributed  to  the  supporting  beams  in  a 
variable  ratio,  increasing  toward  the  center  as  the 
ordinates  of  a  triangle. 

(c)  For  beams  and  girders  the  bending  moments  shall,  aside 
from  loading,  depend  upon  the  end  conditions,  as  given 
above,  under  (a). 


REINFORCED  CONCRETE  81 

(d)  For  slabs  or  beams,  continuous  over  two  spans  only,  or 
for   concentrated   loads,   or   other  unusual   conditions, 
the    moments   and   shears   shall   be    obtained   by '  the 
"  Theorem  of  Three  Moments." 

345.  Resisting  Moments: 

(a)  In  an}*  slab,  beam,  or  girder  reinforced  for  compression 
the  resisting  moment  of  the  steel  in  compression  shall 
equal  the  compressive  value  of  concrete  X 15  X  its  lever 
arm.  (Par.  3486.) 

(6)  In  T-beams,  where  adequate  bond  between  slab  and  web 
of  beam  is  provided,  the  resisting  moment  of  the  top 
flange  of  the  beam  may  include  an  adjacent  part  of 
the  slab.  This  tributary  part  of  the  slab  shall  be  limited 
as  follows: 
To  be  available  the  minimum  thickness  of  slab  shall 

be  one-thirty-second  Qj)  of  the  slab  span. 
The  total  effective  width  shall  not  exceed  one-fourth 

(J)  of  the  span  length  of  the  beam,  or  tw^o-fifths   (-§-) 

of  the   slab  span,  or  8  times  the    thickness  of  slab 

plus  the  thickness  of  web. 

(c)  In  T-beams,  where  the  neutral  axis  falls  below  the  slab, 
the  resistance  of  the  web  shall  be  neglected. 

346.  Reinforced  Columns.     Provision  must  be  made  in  rein- 
forced  columns  for  eccentric   loading,   if  any,   and  for  flexure 
whenever  the  maximum  unsupported  length  of  same  exceeds  18 
diams.     (Par.  348,  c2.) 

Proper  provisions  must  also  be  made  at  the  bottom  of  the 
columns  for  tensile  stresses,  if  any,  and  for  the  distribution,  by 
means  of  bearing  plates  or  otherwise,  of  the  compressive  stresses 
borne  by  the  reinforcement. 

The  live  loads  on  columns  may  be  reduced  according  to 
provisions  in  Par.  96. 

347.  Temperature  Stresses.     Temperature    stresses   shall   be 
calculated,   where  the  structure  cannot  expand    and    contract 
freely,  for  a  variation  of  not  less  than  50°  F.     (Par.  350.) 

UNIT  STRESSES 

348.  Normal   Concrete  and   Structural   Steel.     All   parts   of 
the  reinforced  concrete  structure  shall  be  so  proportioned  that 
the  sum  of  the  maximum  stresses  from  all  causes  shall  not  exceed 


82 


STANDARD  SPECIFICATIONS 


for  normal  concrete  (Par.  375)  reinforced  by  structural  steel 
(Par.  372)  the  following  values  in  pounds  per  square  inch,  except 
as  modified  in  Pars.  349  and  350: 

(a)  Axial  tension: 

Concrete none 

Steel,  net  section 15,000  Ibs.  (40%) 

(6)  Bending : 

Concrete  in  tension none 

"  compression,  generally 600  Ibs.  (30%) 

11 '       "            "          ,  on  bottom  side  of  con- 
tinuous beams  near  support 700  '     (35%) 

Steel  in  tension 15,000  "    (40%) 

"       compression 9,000  " 

[Or  15/c,  where  fc  is  the  allowable  stress  on  the  concrete,  given 
below  under  (c)]. 

(c)  Axial  compression,  on  the  concrete: 

1.  Columns  whose  -j~718  diameters. 
a  ^ 


1.  Columns  whose  -r  <•-  18  diameters  

Up  to  12 
Diam. 

From  12-18 
Diam. 

Plain  concrete  columns 

Lbs. 
500 
500 
600 

750 
750 

% 
25 
25 
30 

37£ 

374- 

Lbs. 
400 
400 
500 

650 
650 

% 
20 
20 
25 

32£ 
32£ 

Columns  with  longitudinal  reinforcement  only  .  . 
'  '     reinforcement  of  bands  or  hoops.  . 
"           "Ion  gitud  inal  reinforcement  of  from 
1—  4%  and  bands  or  hoops       

Columns  reinforced  with  structural  steel  shapes 
thoroughly  encasing  the  concrete  

2.  Columns  whose  -j  >  18  diameters. 
a 


where  fc  =  allowable  unit  stress,  given  above  for  columns  of  12 

diameters  ; 

Z—  unsupported  length  of  column  in  inches; 
d  =  least  width,  or  diameter,  of  effective  area  of  column  in 
inches.     (Par.  359.) 


REINFORCED  CONCRETE  83 

3.  Axial  compression,  on  the  steel. 

Rods,  shapes,  or  built-up  members,  when  reinforcing  the 

concrete lo/c 

Shapes  or  built-up  members  when  independent. 

[See  Pars.  12  (c),  65  (c),  117  (c).] 
(d)  Shear,  on  the  concrete. 

1.  Direct  shear  only  (i.e.,  shear  uncombined  with  either  ten- 
sion or  compression)  for: 

Beams,  having  no  web  reinforcement 40  Ibs.  (2%) 

"     ,      "       bent-up  reinforcement 60   "    (3%) 

"     ,      "       web  reinforcement  of  bent-up 

bars  and  stirrups 120    "     (6%) 


f  One-half   of    compression 

2.  Shear  and   compression  com-  . 

.       ,    •{     values  given  above  un- 
bined,  equal  amount  of  each         .      .  . 

{ Interpolate  between  values 

3.  fehear  and  compression  com-  .  •       /» 

,.»-,»        '    .  1      given  under  (d)  1,  and 

bmed,  other  ratios  7! 

4.  Shear,  on  the  steel  (any  grade) 10,000  Ibs. 

(e)  Diagonal  tension,  on  the  concrete 40  "     (2%) 

•   "     ,  on  the  steel 15,000  ' '  (40%) 

(/)   Bearing. 

Concrete  on  concrete  (equal  areas) ....  500  ' '  (25%) 
(less  area  on 

greater  area)  600  ' '  (30%) 
(g)  Bond  between 

Concrete  and  plain  reinforcing  bars  .  .  80  "  (4%) 

ft    drawn  wire 40    "  (2%) 

"    deformed  bars  (variable)  100-160  "  (5-8%) 


349.  Other  Concretes  and  Steels.  For  concretes,  differing 
in  strength  or  proportion  of  aggregates  from  normal  concrete 
(Par.  375),  substitute  for  values  given  above  (Par.  348)  their 
ultimate  strength  in  28  days  times  percentages  as  indicated,  the 
maximum  increase  over  same  being  limited  to  25  per  cent. 

For  steels,  differing  in  strength  from  structural  steel  grade 
(Par.  193),  substitute  for  tensile  values  given  above  (Par.  348) 


84  STANDARD  SPECIFICATIONS 

40  per  cent  of  their  strength  at  the   yield  point,  as   determined 
by  tests. 

350.  Maximum  Stresses.     When  combining  the  temperature 
stresses  with  stresses  due  to  all  other  causes,  the  specified  unit 
stresses  (Pars.  348,  349)  may  be  increased  10  per  cent,  provided 
that  this  combination  gives  a  greater  sectional  area. 

DESIGN  OF  STRUCTURE 

351.  General  Proportions: 

(a)  The  total  thickness  of  a  slab  shall  not  be  less  than  one- 

thirty-sixth  (-3^-)  of  the  slab  span   in    the    direction  of 
the  principal  reinforcement,  or  less  than  3  in. 

(b)  The  minimum  width  of  web,  in  beams  or  girders,  shall 

not  be  less  than  one-twenty-fourth   (-^y   of    the  span. 
(Par.  342.) 

(c)  The   maximum    diameter   of   reinforcing   rods,   in    slabs, 

beams  or  girders,  shall  not  exceed  one-two-hundredth 
(Ti-0-)   of  the  span. 

352.  Continuous    Spans.      Where    continuity    of    spans,    or 
fixed  ends,  are  depended  upon  and  allowed  for  m  determining 
the  bending  moment  at  center,  the  slab  or  beam  must  be  properly 
reinforced  over  the  supports  to  resist  the  negative  moment. 

353.  Bond   Strength.     Ends   of  plain  reinforcing  bars  must 
be  secured  against  slipping,  either  by  depending  upon  the  bond, 
in  which  case  the  length  of  the  free  end  shall  be  not  less  than 
48    diams.  of   the    rod,  or    by  bending    the    free    end    through 
180°  to   a  radius   of   4  diams.  of  rod,  or  by  an  anchorage   con- 
sisting of  the  free  end  being  upset  and  provided  with  a  nut  and 
a  washer.     The  free  ends  of  stirrups  may,  at  points  where  the 
beam    has    no    top    reinforcement,    be    turned    closely    through 
approximately  360°  for    this    purpose.      At    points   where    top 
reinforcement   exists  the   free   ends    of   the    stirrups   shall   pass 
over  the  same  before  being  so  turned,  or  shall  be  wound  around 
the  bars  approximately  one  and  one-half  (1J)  turns. 

354.  Web   Reinforcement.     After    deducting    the    shear    or 
diagonal  tension   carried  by  the   concrete    (Par.  348d,  348e)  the 
remainder  shall  be  carried  by  reinforcement  consisting  of  bent 
rods  or  stirrups,  or  both.     The  stirrups  shall  be  properly  secured 
against  slipping.     (Par.  353.) 


REINFORCED  CONCRETE  85 

355.  Special  Reinforcement : 

(a)  Rectangular  slabs  reinforced  for  strength  in  one  direction 

only  shall  be  reinforced  in  the  other  direction,  to  prevent 
shrinkage  cracks,  by  rods  not  less  than  f  in.  in  diameter, 
placed  above  the  main  reinforcement  and  spaced  not 
more  than  2  ft.  c.  to  c. 

(b)  Similar  slabs,  designed  for  concentrated  loads,  shall  be 

reinforced  perpendicular  to  the  main  reinforcement 
by  rods  f  in.  in  diameter,  spaced  not  more  than  1  ft. 
c.  to  c.,  to  distribute  such  loading. 

(c)  Slabs,  beams,  or  girders  having  construction  joints  (Par. 

362)  shall  be  provided  with  shearing  rods  proportioned 
to  transmit  shear  due  to  any  partial  loading.  The 
diameter  of  such  shall  not  be  less  than  f  in.,  the  length 
shall  not  be  less  than  96  diameters,  the  spacing  shall  not 
exceed  2  ft.  c.  to  c.,  and  they  shall  be  placed  near  the  top. 

(d)  Reinforcement    against    leakage     cracks,     when    water- 

proofing (Par.  360),  shall  be  distributed  evenly  over 
the  entire  affected  area  and  shall  consist  of  rods  not 
less  than  -|  in.  in  diameter  spaced  not  over  18  in.  c.  to  c. 
in  two  directions  perpendicular  to  each  other, 
(c)  Reinforcement  for  temperature  stresses  (Par.  347)  shall 
be  distributed  over  the  entire  area  of  the  cross-section 
in  a  ratio  varying  with  the  same. 

356.  Splicing  of  Reinforcement.     Wherever  it   is   necessary 
to  splice  the  reinforcement  the  rods  in  tension  shall  be  connected 
by  a  direct  splice  of  a  strength  equal  to  that  of  the  rod,  or  by 
overlapping  their  ends.     The  length  of  lap  in  diameters  shall  not 
be  less  than  the  total  stress  in  the  rod,  at  point  of  splice,  divided 
by  300.     In  compression,  where  reinforcing  rods  over  1  in.  in 
diameter  are  joined,  they  shall  be  butted  and  fully  spliced;  rods 
of  smaller  diameter  may  be  lapped  as  in  tension. 

No  splices  shall  be  made  at  points  of  maximum  stress. 

357.  Minimum    Reinforcement.      The    minimum    reinforce- 
ment in  slabs,  beams  or  girders  shall  not  be  less  than  three- 
fourths  of  1  per  cent  (i%)  of  the  effective  area  of  the  concrete; 
in  columns  with  longitudinal  reinforcement  only  not  less  than 
2  per  cent  and  in  columns  having  circumferential  reinforcement 
such  reinforcement  shall  not  be  less  than  1  per  cent  of  the  effect- 
ive area. 


86  STANDARD  SPECIFICATIONS 

358.  Spacing  of  Reinforcement: 

(a)  Slabs  The  minimum  spacing  of  parallel  bars  shall  not  be 
less  than  3  in.  Two  layers  of  bars  perpendicular  to 
each  other  shall  be  in  contact,  the  bars  forming  the 
main  reinforcement  being  in  all  cases  placed  under- 
most. 

(6)  Beams  and  Girders.  The  minimum  distance  from  the 
center  of  any  bar  to  the  edge  of  beam  shall  be  2  diam- 
eters, or  1^  in.  The  minimum  distance  c.  to  c.  of 
any  bar  in  the  same  layer  shall  be  2£  diameters  for 
round  bars  and  3  diameters  for  square  bars,  and  not 
less  than  2  diameters  between  centers  of  bars  in  different 
layers.  The  longitudinal  spacing  of  stirrups  or  bent 
rods,  where  used,  shall  not  exceed  three-fourths  (f) 
of  the  depth  of  the  beam. 

(c)  Columns.  In  columns  having  longitudinal  reinforcement 
only,  the  rods  shall  be  securely  tied  together  at  inter- 
vals not  exceeding  20  diameters  of  rods.  In  columns 
having  circumferential  reinforcement  the  clear  spacing 
of  such  shall  not  exceed  one-fourth  (J)  the  diameter 
of  the  inclosed  column. 

The  circumferential  reinforcement  shall  be  securely 
held  in  position  by  means  of  spacing  bars,  or  other 
adequate  means. 

359.  Fireproofing.     The  minimum  thickness  of  a  fire -retard- 
ing coating,  covering  the  reinforcement,  shall  be  as  follows: 

For  slabs,  not  less  than  H  diams.  of  rods,  or    f  inch 
"    beams,  1£  ,  or  H    " 

"    girders,  H  ,  or  1J    " 

"    columns,  1J  ,  or  1J-    " 

' ;    columns  having  no  reinforcement,  2     ' i 

The  above  coverings  shall  not  be  considered  as  effective  area; 
they  shall  be  made  of  concrete  in  which  no  limestone  is  used, 
but  in  which  the  coarse  aggregate  may  consist  of  hard-burned 
cinders  or  other  material  that  will  resist  high  temperatures. 
All  aggregates  shall  be  so  small  that  the  reinforcement  is  thor- 
oughly covered,  leaving  no  voids  or  cracks. 

For  further  fire-resisting  purposes  all  external  angles  shall  be 
either  beveled  or  rounded. 


REINFORCED  CONCRETE  87 

360.  Waterproofing.     Waterproofing    shall    be    effected    by 
using  a  concrete  of  maximum  density  in  connection  with  special 
reinforcement    to  prevent  leakage    cracks  (Par.  355d),  or  by  a 
waterproof  coating,  or  by  addition  of  an  approved  waterproof 
compound. 

The  proportion  of  aggregates  to  be  used  in  obtaining  such 
concrete  shall  be  determined  for  each  case  by  experiments. 

The  waterproof  coating  shall  generally  consist  of  from  4  to  8 
layers  of  a  strong  flexible  felt  or  cloth  fabric,  so  treated  in  manu- 
facture that  all  pores  are  closed,  cemented  together  with  specially 
prepared  preparations  of  asphalt,  coal  tar  or  coal-tar  pitch, 
or  of  a  thick  layer  of  a  similar  bituminous  compound  applied  as 
a  mastic,  upon  the  surface  after  being  troweled  off  with  cement 
mortar.  (Par.  377.) 

361.  Weatherproofing.     Concrete  may  be  rendered  weather- 
proof, even  waterproof  under  moderate  pressure,  by  applying 
alternate  washes  of  aluminum  sulphate  and  soap,  or  by  a  wash 
of  cement  grout.      These   washes   shall   be   applied    by  a   soft 
brush   after    the   surface  of  the  concrete    has   been   thoroughly 
cleaned. 

362.  Construction  Joints.     Construction  joints  in  reinforced 
concrete  shall,  whenever  unavoidable,  be  located  as  follows: 

In  slabs  and  beams,  near  the  center  of  the  span. 

In  girders  near  the  center  of  the  span,  except  when  another 

girder  or  beam  joins  at  this  point. 
In    such   case    the   joint  shall  be  offset  a  distance  equal  to 

the  depth  of  the  girder  and  shall  be  reinforced  for  shear 

if  necessary. 
In  columns  horizontal  joints  shall  preferably  be  made  flush 

with  the  lower  side  of  the  girders,  or  the  upper  side  of  the 

floor  line. 
All  const  ruction  joints  in  slabs,  beams,  girders,  or  columns 

shall  be  perpendicular  to  the  plane  of  their  surfaces. 

363.  Expansion  Joints.     In  exposed  work,  when    not    fully 
reinforced    for    temperature    stresses,    special  expansion    joints 
shall  be  provided  at  intervals  usually  not  exceeding  75  ft.     Guides 
for  cracks  shall  be  provided  at  distances  to  be  approved  by  the 
Engineer. 

Expansion  joints  shall  interlock,  wherever  practicable,  usu- 
ally by  tongue-and-groove  joints  in  the  concrete,  reinforced  by 


88  STANDARD  SPECIFICATIONS 

short  steel  rods  embedded  with  one  end  in   the   concrete,   and 
free  to  slide  with  the  other  in  embedded  gaspipe. 


MATERIALS  AND  WORKMANSHIP 

364.  Cement.     The  cement  shall  be  Portland,  either  American 
or  foreign,  which  will  meet  the   requirements  of  the  standard 
specifications    adopted    by    the    American    Society    for    Testing 
Materials.     (See  Part  VIII.) 

365.  Fine  Aggregates.     Fine  aggregates  are  sand  and  screen- 
ings of  either  gravel  or  crushed  stone.     They  shall  be  graded 
in  size  up  to  such  grain  which,  when  dry,  will  pass  a  screen  hav- 
ing l~m.  meshes. 

366.  Coarse    Aggregates.     Coarse    aggregates    most   suitable 
for  reinforced  concrete  structures  are  gravel,  broken  stone,  and 
hard-burned  cinders.     They  shall  be  screened  and  of  such  size 
as  will  be  retained  on  a  screen  having  |-in.   meshes,  but  will 
pass   a   -f-  or  1-in.  mesh,  the   smaller  aggregate   being   used   in 
the    fire-retarding    coating  covering    the   reinforcement.       (Par. 
359.) 

367.  Sand.     The  sand  shall  be  clean,   coarse,   and  of  grains 
varying  in  size.     It  shall  not  contain  clay  or  loam  to  the  extent 
of  more  than  one-half  (i%)  per  cent  and  shall  be  free  from  any 
other  foreign  matter. 

368.  Gravel.     The  gravel  shall  be   composed   of  reasonably 
clean  pebbles  of  hard  and  durable  stones  of  sizes  not  exceeding 
J  in.  in  diameter,  free  from  clay  and  other  impurities.     To  main- 
tain the  proper  proportions  in  the  concrete  mixture  it  shall  be 
screened  and  divided  into  fine  and  coarse  aggregate.     (Pars.  365, 
366.) 

369.  Stone.     The  stone  shall  be  clean,  sound,  hard,  durable, 
and  free  from  all  foreign  matters,  crushed  or  broken  to  sizes 
not  exceeding  1  in.  in  diameter.     Only  such  stones  as  will  break 
in  approximately  cubical  pieces  shall  be  used;    those,  like  slate 
or  shale,  which  break  in  thin  flat  pieces,  shall  be  rejected.     To 
maintain  the   proper    proportions  in  the    concrete    mixture   it 
shall  be  screened   and  divided  into   fine   and   coarse   aggregate. 
(Pars.  365,  366.) 

370.  Cinders.     Hard-burned  cinders  may  be  used  as  the  coarse 
aggregate  of  a  fire-resisting  coating.     (Par.  359.)     They  shall  be 


REINFORCED  CONCRETE  89 

composed  of  hard,  clean,  vitreous  clinker,  free  from  sulphides, 
unbumed  coal,  or  ashes. 

371.  Water.     The  water  shall  be  clean,  free  from  oils,  acids, 
strong  alkalies,  or  vegetable  matter. 

372.  Metal     Reinforcement.     The   reinforcement   shall   pref- 
erably consist    of    structural  steel  conforming  to  the  specifica- 
tions adopted  by  the  Association  of  American  Steel  Manufacturers, 
1910.     (See  Part  V,  Pars.  192  to  201.) 

In  general  round  bars  are  preferable  to  square  bars.  Deformed 
bars  of  hard  steel  and  cold-twisted  bars  may  be  used  in  special 
cases. 

For  the  prevention  of  shrinkage  cracks,  leakage  cracks,  and  as 
reinforcement  for  temperature  stresses,  or  for  minor  details, 
the  bars  used  need  not  be  tested.  All  other  bars  shall  be 
tested. 

373.  Proportions.  ,  The   proportion   of  the   materials  in  the 
concrete  and  the  percentage  of  the  reinforcement  shall  be  specif- 
ically stated  in  the  contract. 

The  aggregates  used  in  the  concrete  shall  be  carefully  selected, 
of  uniform  quality  and  proportioned  so  as  to  secure  as  nearly 
as  possible  a  maximum  density. 

In  ordinary  work  the  proportions  may  be  selected  according 
to  judgment  based  upon  experience;  but  in  important  work, 
or  where  waterproofing  is  required,  the  correct  proportions  for 
maximum  density  shall  be  determined  in  each  case  by  experiments. 

374.  Unit  of  Measure.     The  unit  of  measure  shall  be  the 
barrel,  which  shall  be  taken  as  containing  3.8  cu.  ft.  and  shall 
contain  376  Ib.  of  cement  net.     A  bag  of  cement  shall  contain 
94  Ib.  of  cement  net. 

375.  Normal  Concrete.     For  reinforced  concrete  work  "  nor- 
mal concrete  "  shall  be  composed  of  1  part  Portland  cement  and 
6  parts  of  aggregate,  approximately  2  parts  of  fine  and  approx- 
imately 4  parts  of  coarse  aggregates,  which  shall  be  measured 
separately — capable     of     developing     an     average    compressive 
strength  of  2000  Ib.  per  sq.in.  in  28  days,  when  tested  in  cylin- 
ders 8  in.  in  diameter  and  16  in.  long,  under  laboratory   con- 
ditions of  manufacture  and  storage,  using  the  same  consistency 
as  is  used  in  the  field. 

376.  Other     Concretes.     The    strength    and    suitability    of 
concretes,  other  than  normal  concrete,  for  reinforced  concrete 


90  STANDARD  SPECIFICATIONS 

work  will  depend  upon  the  richness  or  the  leanness  of  the  mixture 
and  the  character  of  the  aggregates. 

The  structural  value  of  such  concretes  shall  be  based  upon 
the  average  compressive  strength  in  28  days,  as  determined  above 
for  normal  concrete.  (Par.  375.) 

377.  Cement   Mortar.      Cement   mortar,   used   in   reinforced 
concrete  work,  shall  generally  be  composed  of  1  part  Portland 
cement  and  from  2  to  3  parts  of  fine  aggregates.     The  mortar 
shall  be  mixed  by  hand.     (Par.  330.) 

378.  Cement     Grout.     Cement     grout,     used     in     reinforced 
concrete  work,  shall  be  composed  of  neat  Portland  cement  mixed 
with  water  to  a  consistency  of  thick  cream  or  whitewash; 

379.  Workmanship: 

(a)  All  material  and  labor  shall  be  of  the  best  quality  in  every 
respect  and  shall  be  subject  to  inspection  and  approval 
at  any  time  during  the  progress  of  the  work. 

(6)  The  entire  work  shall  be  constructed  in  a  substantial 
and  workmanlike  manner,  and  to  the  satisfaction  and 
acceptance  of  the  Engineer.  (Par.  383.) 

(c)  The  contractor  shall  employ  skilled  or  suitable  mechanics 
and  laborers  for  every  kind  of  work  and  shall,  at  the 
request  of  the  Engineer,  discharge  any  workman  whom 
he  deems  incompetent,  negligent,  or  untrustworthy, 

380.  Facing.     (See  Par.  318.) 

381.  Finishing: 

(a)  The  finishing  of  the  surface  shall  be  determined  before 

the  concrete  is  placed  and  the  work  conducted  so  as 
to  make  possible  the  finish  desired. 

(b)  After  the  forms  are  removed  any  small    cavities  or  open- 

ings in  the  face  shall  be  neatly  filled  with  cement  mortar, 
if  necessary  in  the  opinion  of  the  Engineer.  Any 
ridges  due  to  cracks  or  joints  in  the  lumber  shall  be 
rubbed  down  with  chisel  or  wooden  float. 

(c)  When  desired  the  face  may  be  covered  with  a  finish  of  a 

thin  grout,  or  a  whitewash,  applied  with  a  brush. 
Plastering  shall  not  be  applied  to  any  face  exposed  to 
the  weather. 

(d)  Before  the  concrete  has  thoroughly  set  the  face  may  be 

treated  with  a  wire  brush;  after  having  hardened  with 
a  soft  brick,  with  hand  or  pneumatic  tools. 


REINFORCED  CONTRETE  91 

(e)  A  colored  finish  may  be  obtained  by  using  naturally 
colored  aggregates,  or  by  adding  a  mineral  pigment  of 
any  desired  shade  when  mixing  the  concrete,  as  may 
be  determined  by  the  Engineer. 

INSPECTION  AND  ERECTION 

382.  Inspection.     Inspection    during    construction    shall    be 
made   by   competent   inspectors   employed   by,   and   under   the 
supervision  of,  the  Engineer,  and  shall  cover  the  following : 

(a)  The   materials. 

(b)  The  correct  construction  and  erection  of  the  forms  and 

the  supports. 

(c)  The  sizes,  shapes,  and  arrangement  of  the  reinforcement. 

(d)  The  proportioning,  mixing,  and  placing  of  the  concrete. 

(e)  The  strength  of  the  concrete  by  tests  upon  standard  test 

pieces  made  on  the  work. 
(/)  The  protection  of  the  work  against  frost,  the  sun  and  the 

weather  generally. 
(g)  Whether  the  concrete  is  sufficiently  hardened  before  the 

forms  and  supports  are  removed. 
(h)  Prevention  of  injury  to  any  part  of  the  structure  by  and 

after  the  removal  of  the  forms  and  shores, 
(i)  Comparison   of   dimensions   of   all  parts   of   the   finished 

structure  with  the  plans. 

383.  Accepting  Material  or  Work.     If  the  inspector,  through 
an  oversight  or  otherwise,  has  accepted  material  or  work  which 
is  defective   or  contrary  to  the  specifications,  the  material  or 
work,  no  matter  in  what  stage  of  completion,  may  be  rejected 
by  the  Engineer. 

384.  Testing  the  Structure.     Load  test  on  any  part  of  the 
finished  structure  shall  be  made  where,  in  the  opinion  of  the 
Engineer,  there  is  a  reasonable  suspicion  that  the  work  has  not 
been  properly  performed,   or  that,  through  influences  of  some 
kind,  the  strength  has  been  impaired,  and  may  be  made  in  any 
case. 

The  test  load  applied  shall  not  exceed  that  which  will  cause 
a  total  stress  in  the  reinforcement  of  three-fourths  (J)  of  its 
strength  at  the  yield  point,  or  more  than  twice  the  superimposed 
load. 


92  STANDARD  SPECIFICATIONS 

The  test  load  shall  be  left  on  the  part  under  test  for  24  hours , 
shall  not  cause  a  deflection  exceeding  one-four-hundred-and- 
eightieth  Criir)  of  the  span,  shall  show  no  sign  of  cracks,  and 
shall  leave  no  permanent  deformation. 

Load  tests  shall  not  be  made  upon  arches  until  after  90  da'ys, 
or  upon  other  structures  until  after  60  days,  of  hardening. 

385.  Erection: 

(a)  Whenever  the  contractor  is  required  to  remove  any 
existing  structure,  to  clear  the  site,  or  to  excavate,  such 
requirements  shall  be  specifically  stated  in  the  con- 
tract. 

(6)  Otherwise  the  erection  shall  include  all  necessary  hauling, 
the  unloading  of  the  materials  and  their  proper  care 
until  the  completion  and  acceptance  of  the  work,  as 
specified  in  Pars.  385c  to  391. 

(c)  The  contractor  shall  furnish,  at  his  own  expense,  all 
necessary  staging,  falsework,  materials,  and  tools,  and 
shall  erect  the  structure  complete  and  finish  the  same 
as  specified  in  the  contract.  (Par.  390.) 

386.  Removal  of  Old  Structure.     Whenever  new  structures 
are  to  replace  existing  ones  the  latter  shall  be  carefully  taken 
down  and  removed  by  the  contractor  to  some  place  specified 
in  the  contract. 

387.  Interruption  of  Traffic.     All  operations  shall  be  so  con- 
ducted as  not  to  impede  or  interrupt  the  work  of  other  contrac- 
tors, the  traffic  of  any  railroad,  nor  close  any  thoroughfare  or 
waterway,  nor  conflict  with  any  law,   regulation,  or  ordinance 
of  any  properly  constituted  authority. 

388.  Permits.     Before    commencing   operations   the   contrac- 
tor shall,  at   his  own  expense,  obtain  all  necessary  permits  and 
comply  with  their  requirements. 

389.  Safeguards  and  Damages.     The  contractor  shall  furnish, 
at  his  own  expense,  all  watchmen,  guards,  signals,  night  lights, 
etc.,  for  the  prevention  of  accidents,  and  be  responsible  for  the 
safety  of  the  structure;  and  he  shall  assume  full  responsibility 
for  all  accidents  to  men,  animals,  and  materials  before  the  com- 
pletion and  final  acceptance  of  the  structure  and  shall  indemnify 
its    owner  for   any  and   all   claims   for   damages   arising   there- 
from. 

390.  Defective    Work.     The    contractor    shall,    at    his    own 


REINFORCED  CONCRETE  93 

expense,  remove,  rebuild,  or  make  good  any  damaged  material 
or  defective  work,  even  if  same  through  an  oversight  or  other- 
wise has  been  previously  accepted. 

391.  Clearing  up.  When  the  erection  is  completed  the  con- 
tractor shall,  at  his  own  expense,  remove  all  falsework,  rubbish, 
and  other  useless  material  caused  by  his  operations. 


INDEX 


REFERENCES  ARE  TO  PARAGRAPHS,  NOT  PAGES 


A  CCEPTING  materials  or  work,  244, 
"     383 

access  to  mills,  240 
"       "  shops,  243 
aggregates,  coarse,  366 

,  fine,  365 
allowable  variation,  177 

in   weight,    188, 
189 

all  structures,  86,  133 
alternate  stresses,  122 
analysis,  chemical,  181 
anchor  bolts,  46 
annealed  specimens,  183 
annealing,  232 

approaches  for  highway  bridges,  58 
assembling,  220 

T>ASES  for  columns,  45,  101 
•*-^     beam  girders,  28 
bearing  power  of  piles,  21 
bearings  for  bridges,  151,  231 
"    girders,  151,  173 
bending  tests,  179 
bends,  nicked,  180 
bond  strength,  353 
bolts,  anchor,  46,  148 

"    ,  turned,  218 
bracing,  25,  83,  131,  168 
bridges,  beam-,  79,  125,  127 

"      ,  deck,  81,  129 

' '      ,  pony,  80,  128 

"      ,  skew,  158 

"      ,  through,  82,  130,  157 

"      ,  type  of,  50 
burrs,  213 

CAMBER,  103,  150 
cast  iron,  17,  190 
cast  steel,  70,  233 
ceiling,  272 
cement,  288-306,  364 


cement,  constancy   of   volume,    293, 

299,  305 

"      ,  definition  of,  295,  300 
"      ,  fineness  of,  290,  296,  302 
' '      ,  f  or  concrete,  307 
' '      ,  general  conditions,  294 
"      ,  grout,  378 
"      ,  magnesia  in,  306 
"      ,  mortar,  377 
' '      ,  natural,  295-299 
"      ,  Portland,  300-306 
' '      ,  specific  gravity  of,  289,  301 
"      ,  sulphuric  acid  in,  306 
"      ,  time    of    setting,    291,    297, 

303 
"      ,  tensile  strength  of,  292,  298, 

304 

centrifugal  force,  63,  116 
chemical  analysis,  181,  194 
cinders,  370 

classification  of  highway  bridges,  49 
cleaning,  249 

clearances,  in  bridges,  52,  106 
clearing  up,  263,  391 
columns,  9,  41,  346 
column  bases,  45,  101 
combined  stresses,  14,  71,  124 
compression  flange,  163 

members,  39,  96,  143 
concrete,  normal,  375 
"       ,  other,  376 

,  placing  of,  333 
condition  of  surfaces,  252 
connection  angles,  209 

,  details  of,  32,  89,  136 
,  field,  208 

contact  surfaces,  "250 
copies  of  mill  orders,  238 
counter  stresses,  123 
covering,  roof,  3 
crane  loads,  10 
cross  ties,  :N:-> 

95 


96  INDEX 

REFERENCES  ARE  TO  PARAGRAPHS,  NOT  PAGES 


TTVAMAGES,  safeguards  and,  261,  389 
*-*     dead    loads,  1,  2,  3,  4,    5,    59, 

109,  154,  336 
deck  bridges,  81,  129 
defective  material,  187 

work,  262,  390 
depositing  concrete,  316 
design  of  flanges,  160 
"       "  plate  girders,  159 
"       "  web,  165 

details  of  connections,  32,  89,  136 
"  joints,  31,  88,  135 


stresses,  15,  72 
-        edge  distance  of  rivets,  35,  140, 

172 

edge  planing,  206 

elongation,  modification  in,  178,  198 
erection,  256-264,  385 

'  '        by  purchaser,  264 
expansion   joints    in  concrete,    317, 

363 

rollers,  13,  48,  69 
eye-bars,  37,  94,  142,  224,  225 
eye-bar  tests,  248 

TTiACiLiTiES  for  mill  inspection,  239 
•*-      facilities    for    shop    inspection, 

241 

facing  concrete,  318,  380 
field  connections,  208 

"  rivets,  217 
fillers,  220 
finish,  185,  205,  207 
finishing  concrete,  320,  381 
fireproofing,  359 
flanges,  compression,  163 

'  '      ,  design  of,  160 

"      ,  plates,  161 

'  '      ,  rivets,  164 

'  '      ,  splices,  162 
floor  framing,  77,  126 
flooring,  timber,  271,  278,  279 
floors,  live  loads  on,  9 

'  '     ,  paved,  53 

11     ,  wooden,  271,  279,  280,  281 
force,  centrifugal,  63,  116 
"    ,  lateral,  113 
"    ,  traction,  64,  115 
form  of  specimens,  182,  196 
forms  for  concrete,  315,  326,  335 
foundation,  pressure  on,  19,  66,  118 
reezing  weather,  322,  334,  335 


/GIRDER,  beam,  28 

^     girder,  design  of,  159 

girder,  plate,  153,  174 

girts,  27 

general  dimensions,  342 

"       proportions,  76,  125,  156 

"       requirements,     49-58,     105- 
108,  153 

"       workmanship,  202 
gravel,  310,  368 
grout,  378 
guard  rails,  284 

"     ,  wheel,  281 

TTAND  railing  for  bridges,  57,  282 
-*"*-     heavier  loading,  111 

TNACCESSIBLE  surfaces,  251 
•*•     ingredients  in  concrete,  329 
inspection,  238-248,  382  . 
interruption  of  traffic,  258,  387 
impact,  11,  61,  112,  341 
iron,  cast,  17,  190 
"   ,  wrought,  191 

JOINTS,  details  of,  31,  88,  135 

^      joints,    expansion    in    concrete, 

317,  363 

joints,  finish  of,  207 
joists,  timber,  278,  280 

LATERAL  forces,  113 
lattice-bars,  42,  145,  204 
load,  crane,  10 
"   ,dead,  1,2,3,  4,  5,  59,  109,  154, 

336 

"   ,  live,  9,60,  110,  111,  340 
"   ,  snow,  6 

"lyTACHiNE-finished  surfaces,  253 
•"•*•     manufacture,   process   of,   175, 

192 

material  for  buildings,  3,  4,  5 
"    bridges,  51,  105 
' '    concrete  reinforcing  bars, 

192-201 

' '    rivet  steel,  175-189 
"         "    structural  steel,  175-189 
"       ,  defective,  187 
maximum  stresses,  73,  350 
mill,  access  to,  240 
' '      inspection,  facilities  for.,  239 


INDEX 
REFERENCES  ARE  TO  PARAGRAPHS,  NOT  PAGES 


97 


mill  orders,  copies  of,  238 
minimum  size  of  material,  30,  87,  134, 

169 

mixing  concrete,  312,  313 
modification  in  elongation,  178,  198 
mortar,  cement,  377 

NATURAL     cement,     constancy    of 
volume,  299 
natural  cement,  definition,  295 

11      ,  fineness,  296 
"  "      ,  tensile  strength,  298 

"  "      ,  time  of  setting,  297 

nicked  bends,  180 
number  of  tests,  184,  197 
"  twists,  199 

"PAINTING,  249-255 

•£        "       ,  after  erection,  255 

"       ,  omitted,  254 
paved  floors,  53 
permits,  259,  388 
pin  holes,  44,  147,  226,  227 
pins,  43,  146,  228 
piles,  bearing  power  on,  21 
' '    ,  specification  for,  270 
' '    ,  trestles,  285 
"    .  unit  stresses  for,  277 
pilot  nuts,  229 
pitch  of  roofs,  24 
planks,  273 
pony  bridges,  80,  128 
Portland  cement: 

constancy  of  volume,  305 

definition,  300 

fineness,  302 

magnesium  in,  306 

specific  gravity,  301 

sulphuric  acid  in,  306 

tensile  strength,  304 

time  of  setting,  303 
Portland-cement  concrete: 

cement  for,  307 

consistency,  314 

depositing,  316 

expansion  joints  in,  317 

facing,  318 

finishing  of.  320 

forms  for,  315 

freezing  weather,  322 

gravel  for,  310 

mixing  by  hand,  312 

"   machine,  313 


Portland-cement,  proportions  of,  319 
sand  for,  308 
stone  for,  309 
water  for,  311 
waterproofing  of,  321 
pressures,  on  foundations,  19,  66, 118 
"        ,  on  soils,  20 
' '       ,  on  walls,  18 
process  of  manufacture,  175,  192 
proportions,  general,  76,  125,  156 
"  of  concrete,  319,  351 

punching,  211,  212 

TJEAMING,  212,  214 
•^  Reinforced  concrete: 

accepting  material,  383 

' '         work,  383 
adherence  to  plans,  325 
aggregate,  coarse,  366 

,  fine,  365 
assumptions,  343 
bending  moments,  344 
bond  strength,  353 
cement  for,  364 

' '      -grout,  378 

"      -mortar,  377 
centrifugal  force,  338 
cinders,  370 
clearing  up,  391 
columns,  346 
construction  joints,  362 
continuous  spans,  352 
damage,  389 
dead  load,  336 
defective  work,  390 
erection,  385 
expansion  joints,  363 
facing,  380 
finishing,    381 
fireproofing  of,  359 
freezing  weather,  334 
general  dimensions,  342 

"     •  proportions,  351 
gravel,  368 
impact,  341 
ingredients  for,  329 
inspection,  382 
interruption  of  traffic,  387 
live  loads,  340 
maximum  stresses,  350 
minimum  reinforcement,  357 
metal  reinforcement,  327,  372 
mixing  by  hand,  312,  330 


98  INDEX 

REFERENCES  ARE  TO  PARAGRAPHS,  NOT  PAGES 


reinforced  concrete,  maxing  by  ma- 
chine, 313,  331 
normal  concrete,  348,  375 
other  concretes,  349,  376 

' '      steels,  349 
permits,  388 
placing  of  concrete,  333 
"        "  forms,  326 
"        "  reinforcement,  328 
preparations  of  plans,  324 
proportions,  373 
removal  of  forms,  335 

"        "  old  structures,  386 
resisting  moments,  345 
safeguards,  389 
sand  for,  367 

spacing  of  reinforcement,  358 
special  reinforcement,  355 
splicing  of  reinforcement,  356 
stone  for,  369 
temperature  stresses,  347 
testing  the  structure,  384 
traction  force,  339 
unit  of  measure,  374 
unit  stresses,  348 
water  for.  372 
waterproofing  of,  360 
web  reinforcement,  355 
weatherproofing  of,  361 
wind  pressure,  337 
workmanship,  379 
removal  of  old  structures,  257,  386 
requirements,  schedule  of,  176,  193 
reversal  of  stresses.  16,  74 
riveted  work,  90,  137 
rivet  holes,  210 
riveting,  219 
rivets,  33,  87,  138,  170 
"     ,  edge  distance  of,  35,  140 
"     ,  field,  217 
' '     ,  how  driven,  216 

in  flanges,  164 
' '     ,  size  of,  215 
"     ,  spacing  of,  34;  139,  171 
rods,  38,  95 

rollers,  expansion,  13,  48,  69,  228 
roof,  bracing  of,  25 
"  covering,  3 
' '   ,  design  of,  22 
' '   load,  8 
' '    ,  pitch  of,  24 
roof  trusses,  spacing  of,  23 
"      ,  weight  of,  5 


SAFEGUARDS     and     damages,     261, 

^     389 

sand,  308,  367 

scantling,  273 

schedule  of  requirements,  176,  193 

screw  threads,  230 

shingles,  269 

shipping  details,  235 

'  '         invoices,  246 
shop  inspection,  facilities  for,  241 

1  '     plans,  245 
shops,  access  to,  243 

"     ,  starting  work  in,  242 
skew-plate  girder  bridges,  158 
snow  load,  6. 
soil,  pressure  on,  20 
spacing  of  rivets,  34,  139 
specimen,  annealed,  183 

'     "        ,  form,  of,  182,  196 
splices  in  flanges,  162 
"       "  plates,  222 

"  web,  166 
stamping,  186 
steel,  cast,  70,  233 
'  '    ,  cold-twisted,  193 
"    ,  hard-grade,  193 
'  '    ,  structural,  175-189 

-grade,  193 
"    ,  trestles,  84,  132 
stiffeners,  web,  167 
stone,  309,  369 
straightening  material,  203 
stresses,  alternate,  122 

"      ,'  combined,  14,  71,  124 
"       ,  counter,  123 
'  '       ,  eccentric,  15,  72 
'  '      ,  maximum,  73 
'  '      ,  reversal  of,  16,  74 
stringers,  in  trestles,  287 
structures,  all,  86,  133 
sub-punching,  212 
surfaces,  condition  of,  252, 
"       ,  inaccessible,  251 
"       ,  machine-finished,  253 

47,    104,    152,    174, 


347 

tension  members,  36,  93,  141 
testing  the  structure,  384 
tests,  bending,  179 
"    ,  eye-bars,  248 
'  '    ,  number  of,  184,  197 
"    ,  to  prove  workmanship,  247 


INDEX 


99 


REFERENCES  ARE  TO  PARAGRAPHS,  NOT  PAGES 

TTARiATioxs,  allowable,  177 
V      variations,  in  pin  holes,  227 
variations,     in    weight,     188,      189, 
201 


tie-plates,  40,  144 

ties,  cross,  283 

through  bridges,  80,  130,  L~>7 

timber,  dimension,  274 

"      ,  dressing  of  sawed,  268 

"      ,  flooring,  271,  278,279 

"      ,  joists,  278,  280 

* '      ,  kinds  of,  265 

' '      ,  quality  of,  266 

' '      ,  size  of  sawed.  267 

"      ,  unit  stresses  in,  275.  L' 

traction  forces,  64,  115,  339 

traffic,  interruption  of,  258 

trestles,  column  bases  for,  101 
' '      ,  pile,  285 
"      ,  steel,  84,  132 
"      ,  wooden,  285,  286,  287 

trusses,  roof,  design  of,  22 
"  ,  ' '  ,  spacing  of,  23 
"  "  ,  weight  of  5 

turned  bolts,  218 

type  of  bridge,  50 

twists,  number  of,  199 


U 


NIT  stresses: 

in  bridges,  65,  117,  155 

in  buildings,  12 

in  cast  iron,  17 

in  cast  steel,  70 

in  piles,  21,  277 

in    reinforced    concrete, 

349,  350 
in  timber,  275,  276 


348, 


WALL  plates,  45 
wall  plates,  pressure  on,  18 
wainscoting,  272 
water,  311,  372 
waterproofing,  321,  361 
weatherproofing,  362 
web,  design  of,  165 
"   ,  plates/  221 
"   ,  reinforced,  354 
"   ,  splices,  166 
"   ,  stiff  eners.,  167,223 
weight,  236,  237 
welds,  234 
wheel  guards,  281 
wind      pressure,     on      bridges, 

114 

"  (t         ,  on  buildings,  7 

wooden  floors,  271,  279.  280,  281 

trestles,  285,  286,  287 
worTc,  defective,  262 

"    ,  riveted,  90,  137 
workmanship,  202-248,  379 
wrought-iron  bars,  191 

\7"iELD  point.  176.  195 


62 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 
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